Valdura Saks

Cinderalla Solution

Metabolic Weight Loss

Get Instant Access

Laboratory of Bioenergetics, Institute of Chemical and Biological Physics, Tallinn,

Estonia

1. Introduction 65

2. The role of the outer mitochondrial membrane in restricting ADP diffusion and controlling respiration 66

3. Metabolic oscillations in cytoplasm as a feedback signal 72 References 76

Key words: adenine nucleotides, cardiomyocytes, compartmentation, creatine kinase, diffusion, free energy exchange, mitochondria, oxidative phosphorylation, regulation

1. INTRODUCTION

The creatine kinase (CK) isoenzymes function, in vivo, coupled to intracellular structures (mitochondria, myofibrils and cellular membranes). They operate at equilibrium in the cytoplasm as part of the intracellular creatine phosphate (PCr) pathway, or "phosphocreatine circuit" for energy channelling (Saks et al., 1978, 1991a; Bessman and Geiger, 1981; Bessman and Carpenter, 1985; Jacobus, 1985; Wallimen et al., 1992; Wegmann et al., 1992; Wyss et al., 1992; Aliev and Saks, 1993). Chapters 1,2 and 4 provided an introduction to the CK system. We will now see how compartmentalization of CK enzymes are involved in cardiac energy metabolism.

Very recent experimental work with membrane permeabilized (or "skinned") cells has shown that besides an energy transport function the CK system may also regulate cellular respiration as a result of the retarded or

Creatine and Creatine Phosphate:

Scientific and Clinical Perspectives ISBN 0-12-186340-9

Copyright © 1996 Academic Press Limited All rights of reproduction in any form reserved

Figure 5.1. (A) The dependence of the rate of respiration of the skinned cardiac fibres on the external ADP concentration in the absence (curve 1) and in the presence of 25 mm creatine (curve 2). (B) Linearization of the dependency shown in Fig. 5.1 A in the double reciprocal plots. Note the change in the value of apparent K^ for ADP by creatine at constant Vm .

Figure 5.1. (A) The dependence of the rate of respiration of the skinned cardiac fibres on the external ADP concentration in the absence (curve 1) and in the presence of 25 mm creatine (curve 2). (B) Linearization of the dependency shown in Fig. 5.1 A in the double reciprocal plots. Note the change in the value of apparent K^ for ADP by creatine at constant Vm .

restricted diffusion of ADP inside the cells (Saks et al., 1991a,b, 1993). These data are outlined and explained in this chapter. An hypothesis based on local oscillating changes of ADP and creatine concentrations and a feedback signal between contraction and respiration in heart and skeletal muscle is also introduced.

2. THE ROLE OF THE OUTER MITOCHONDRIAL MEMBRANE IN RESTRICTING ADP DIFFUSION AND CONTROLLING RESPIRATION

Experimental results using saponin-skinned fibres (where all the cells have had their sarcolemma removed but intracellular structures preserved) are shown in Fig. 5.1. The respiration rate of the mitochondria is measured with increasing ADP concentrations (Saks et al., 1991a,b, 1993) and the maximal rate of respiration is achieved only at millimolar external ADP concentrations, as shown by curve 1 of Fig. 5.1 A. However, the rate of respiration at any ADP concentration accelerates significantly in the presence of creatine (curve 2 of Fig. 5.1 A) owing to mitochondrial CK activation (Sakseia/., 1991a, b, 1993).

The stimulation of respiration is due to a significant decrease in the apparent Km for ADP at constant Kmax (Fig. 5.1B). However, when these experiments are repeated in the presence of 125 mm KCl (which is known to release mitochondrial CK from the inner membrane), the stimulating effect of creatine on respiration disappears completely (Saks et al., 1995). Such stimulation by creatine depends on functional coupling of mitochondrial CK to the adenine

(A) Electron micrographs of the cardiac fibres. Control, magnification

Figure 5.2.

50000 X.

(A) Electron micrographs of the cardiac fibres. Control, magnification

Figure 5.2. (B) After saponin treatment. The phospholipid bilayer of the sarcolemma is destroyed and vesicularized, but intracellular structures - mitochondria and myofibrils - are normal and have an appearance characteristic for these structures in the hyperosmotic physiological salt solution.
Figure 5.2. (C) Fibres after 30 min in the 40 mOsM solution, 54000 x. For control before osmotic shock, see Fig. 5.3B. Mitochondrial outer membrane rupture is obvious, but the mitochondrial population with the well-preserved outer membranes is seen.

nucleotide translocase. We have shown that detachment of mitochondrial CK from the inner mitochondrial membrane abolishes the functional coupling between mitochondrial CK and adenine nucleotide translocase (Saks et al., 1993). Thus, the stimulating effect of creatine on the respiration of saponin-skinned cardiac fibres seems to be directly related to tight functional coupling between these two proteins. This coupling involves some restriction of diffusion of ADP - or substrate channelling.

In order to determine which cellular structures might be responsible for the retarded diffusion of ADP and the cause of this very high apparent Km, saponin-skinned fibres were treated with 0.8 M KCl to solubilize thick filaments (myosin) and to obtain so-called "ghost" fibres (Saks et ah, 1993). Using conditions of mitochondrial swelling in a hypo-osmotic medium (Stoner and Sirak, 1969; Kuznetsov et al., 1989), disruption of the outer mitochondrial membrane was achieved in isolated mitochondria as well as in the saponin-skinned cardiac fibres. Thus, experiments were performed with thick filaments removed or with the outer mitochondrial membrane functionally removed. It was then possible to determine which of these structures affected ADP's ability to stimulate respiration. Further experiments were also performed with morphological and biochemical analysis to determine the extent of outer mitochondrial membrane disruption (Saks et al., 1991a,b, 1993).

Incubation of skinned heart fibres in a 40 mOsM solution produces marked outer mitochondrial membrane disruption (Fig. 5.2) as shown in electron

Figure 5.3 The oxygraph traces of recording of the respiration of skinned cardiac fibres before (1) and after (2) osmotic shock in the 40 mOsM solution. The respiration rates were recorded in the medium containing 125 mM K.C1 to detach the cytochrome c from the membrane and in this way to test the intactness of outer mitochondrial membrane. CAT, carboxyatractylaside.

Figure 5.3 The oxygraph traces of recording of the respiration of skinned cardiac fibres before (1) and after (2) osmotic shock in the 40 mOsM solution. The respiration rates were recorded in the medium containing 125 mM K.C1 to detach the cytochrome c from the membrane and in this way to test the intactness of outer mitochondrial membrane. CAT, carboxyatractylaside.

micrographs. However, significant areas of preserved outer membrane can also be observed. After hypo-osmotic treatment there are several populations of mitochondria in the skinned fibres - those with intact and those with interrupted membranes. In order to get a rough estimate of the ratio of these populations the cytochrome c test was used; the results are shown in Fig. 5.3. It shows that before hypo-osmotic treatment (trace 1), addition of exogenous cytochrome c has no effect on the respiration of skinned fibres at maximal ADP concentrations. This relates to the intact outer membrane (endogenous cytochrome c is not released and conversely the exogenous cytochrome c cannot enter). However, after hypo-osmotic shock, the maximal rate of respiration is significantly decreased (trace 2) but can be restored by adding exogenous cytochrome c (8 /am). This shows that about half of the mitochondrial population has disrupted outer membranes under these conditions.

A kinetic analysis of ADP-dependence of respiration in "ghost fibres" (after removal of myosin) (Fig. 5.4) illustrates no difference between the experimental Km before (curve and line 1) and after (curve and line 2) myosin thick filament dissolution. In both cases, the value of the apparent Km for ADP is high (381 ±67 /am). Thus, the binding of ADP to myosin ATPase fails to explain the retarded ADP diffusion because the presence or absence of myosin did not change the affinity (Km) for ADP (Kuznetsov et ah, 1989; Saks et ah, 1991a,b, 1993).

25

B

20

-

15

/

o

>

10 5

iiii

Figure 5.4 (A) The dependence of the respiration rate of the skinned and "ghost" fibres on the external ADP concentration. 1, control, skinned fibres; 2, ghost fibres, obtained after treatment of skinned fibres with 800 mm KC1 solution.

Figure 5.5 (A) The dependency of respiration rate on the external ADP concentration of the skinned cardiac fibres before (curve 1) and after (curve 2) osmotic shock in the 40 mOsM solution. (B) Linearization of the dependency shown in Fig. 5.5A in the double reciprocal plots. 1, control; 2, after osmotic shock in the 40 mOsM solution. In the latter case two different kinetics are seen corresponding to two populations of mitochondria with disrupted and intact outer membranes (Figs 5.3A and C respectively).

Figure 5.5 (A) The dependency of respiration rate on the external ADP concentration of the skinned cardiac fibres before (curve 1) and after (curve 2) osmotic shock in the 40 mOsM solution. (B) Linearization of the dependency shown in Fig. 5.5A in the double reciprocal plots. 1, control; 2, after osmotic shock in the 40 mOsM solution. In the latter case two different kinetics are seen corresponding to two populations of mitochondria with disrupted and intact outer membranes (Figs 5.3A and C respectively).

As shown in Fig. 5.5A, osmotic shock destroys the outer mitochondrial membrane and significantly changes the dependence of the rate of respiration upon external ADP concentration. At low [ADP], respiration is higher after osmotic shock (Fig. 5.5B). In this figure two lines are shown, reflecting two regulatory processes in these fibres, one characterized by a high apparent Km for ADP equal to that of fibres before osmotic shock, and a second process with an apparent Km for ADP of 35 /xM (which is close to that for isolated mitochondria or for those lacking the outer membrane, see Table 5.1).

The results demonstrated in Figs 5.4 and 5.5 have led to the conclusion that

Table 5.1 Apparent Km values for ADP in regulation of respiration in different preparations at pH 7.2.

Preparation -Creatine + Creatine

Table 5.1 Apparent Km values for ADP in regulation of respiration in different preparations at pH 7.2.

Preparation -Creatine + Creatine

1.

Skinned cardiac fibres

263.7±57.4

79±8

2.

Skinned cardiac fibres in KC1,125 mm

225±25

354±7.5

3.

Skinned skeletal muscle fibres

334±54.2

105±14.9

4.

Ghost cardiac fibres (without myosin)

381 ±67

5.

Skinned cardiac fibres with

I II

swollen mitochondria"

315±23 32.3±5

6.

Isolated mitochondria

Heart

17.6±1.0

13.6+4.4

Liver

18.4

"I, control; II, osmotic shock.

"I, control; II, osmotic shock.

the outer mitochondrial membrane is an important intracellular structure which retards ADP diffusion out of the intermembrane space (Kuznetsov et al., 1989; Saks et al, 1993). In the isolated mitochondria (with morphologically intact outer membrane), however, the outer mitochondrial membrane barrier function is less evident (see Table 5.1).

The high outer membrane permeability of isolated mitochondria in vitro to low molecular weight substances is well recognized. When first observed, it was assumed that this was just a "leaky" membrane phenomenon. Detailed studies since the mid-1980s, from several laboratories, have shown that the high permeability is due to the existence of protein pores, or voltage-dependent anion selective channels (VDAC) with pore size in the range 2 /jlM (Colombini, 1987; de Pinto et al, 1987; Mannella and Tedeschi, 1987; Tedeschi and Kinnally, 1987; Zimmerberg and Parsegian, 1987; Kayser et al., 1988; Kottke et al., 1988; Benz et al., 1990; Liu and Colombini, 1991). The 35 kD protein forming these pores has been isolated from different sources and characterized and cloned. In a series of publications from the laboratories of Brdiczka and Wallimann (Kottke et al., 1988; Brdiczka, 1991; Wallimann et al., 1992), the mitochondrial porin channels have been shown to be involved in forming dynamic contact sites between the inner and outer mitochondrial membranes. Particularly interesting is the participation of the cubic mitochondrial CK octamers at these contact sites. Such a supramolecular complex of porin-CK-adenine nucleotide translocase assumes direct channelling of substrates (ATP and ADP) and very efficient creatine phosphate (PCr) production from nascent mitochondrial ATP and cytoplasmic creatine (Saks et al., 1978; Wyss et al., 1992).

These results (Kuznetsov et al., 1989; Saks et al., 1991a,b, 1993) demonstrate the role of the outer mitochondrial membrane in regulating the diffusion of

ADP from the cytoplasm into the intermembrane space in vivo. Even though isolated mitochondria have morphologically well-preserved membranes, they have a high permeability to ADP (Kuznetsov et al., 1989; Saks et al., 1993). In vivo, however, mitochondrial membrane permeability is low. Thus, it is apparent that there are important regulatory factors acting on the VDAC permeability to ADP inside the cells. It is most probable that there exists an as yet unknown intracellular factor associated with the outer membrane in vivo, which controls permeability.

In living cells, the oncotic pressure which develops as a result of the high cytoplasmic protein concentration might be an additional factor decreasing the VDAC permeability for ADP. This means that at physiological ADP concentrations the outer membrane may be a significant barrier for ADP and thus cause diffusion limitations. This striking difference in vitro compared with in vivo, between the functional behaviour of the mitochondria with respect to ADP (see Table 5.1), supports Sjostrand's observations (1978). He studied the mitochondrial membrane system in vivo and in vitro under carefully controlled conditions using tissue fixation. Our recent work indicates that a very limited amount of cytoplasmic ADP crosses the outer mitochondrial membrane of the cells in vivo to activate oxidative phosphorylation [remember oxidative phosphorylation is coupled to the CK reaction (Kuznetsov et al., 1989; Saks et al., 1993; and see Chapter 4)]. This reaction is a powerful amplification mechanism regulating and controlling the rate of oxidative phosphorylation (Fig. 5.1). To act as a control mechanism, mitochondrial CK resides at the outside of the inner membrane to ensure direct substrate channelling (Wyss et al., 1992).

3. METABOLIC OSCILLATIONS IN CYTOPLASM AS A FEEDBACK

SIGNAL

The estimated concentration of free ADP in the cardiac cell cytoplasm of the normal heart is around 30-50 ¡xm (Heineman and Balaban, 1990; Balaban et al., 1986; Balaban, 1990; Katz et al., 1987, 1989; Veech et al., 1979). Several investigators (Balaban et al., 1986; Balaban, 1990; Katz et al, 1987, 1989; Veech et al., 1979) have pointed out that this ADP concentration exceeds the Km for ADP found in isolated mitochondria (about 17 ¡jlM) (Chance and Williams, 1955, 1956; Kuznetsov et al., 1989). If this Km applied in vivo, then the calculated ADP would keep the rate of respiration constantly close to maximum. However, the respiration rate is not this rapid in vivo (Balaban et al., 1986; Katz et al., 1987, 1989; Heineman and Balaban, 1990; Balaban, 1990). If the value of the Km for ADP found in this work for cardiomyocytes is used (300 ¡jm), the cytoplasmic concentration of 50 ¡jlM ADP gives a respiration rate of not more than Vn of Fmax. Obviously, if the ADP flux is an order of magnitude slower than that required for maximal respiration, then even activation of the Krebs cycle and of the respiratory chain by calcium (Hansford, 1985; Katz etal., 1987; Balaban, 1990; McKormacei a/., 1990) will not be sufficient to reach maximal respiration. Therefore, under these conditions, ADP supply will become the rate-limiting factor during periods of increased work, providing there is no system for regenerating ADP in the intermembrane space

If the Km were to be 300 /am a dilemma arises with respect to ADP production, because in order to supply enough ADP to the adenine nucleotide trans-locase for maximal respiration (remembering the very low permeability of the outer membrane for ADP), ADP would have to be generated between the outer and inner membranes, in the so-called intermembrane space. This would occur in response to some stimulus from the cytoplasm and candidates for this role are CK and adenylate kinase (Saks et al., 1978; Bessman and Geiger, 1981 ; Bessman and Carpenter, 1985; Kottkeeia/., 1988; Brdiczka, 1991; Wallimann et al., 1992). In muscle cells, the dominating ADP-producing system may belong to the CK system.

The PCr pathway (Saks et al., 1978; Bessman and Geiger, 1981; Bessman and Carpenter, 1985; Wallimann et al., 1992) [("circuit" according to Wallimann et al. (1992) and Wyss et al. (1992) and "shuttle" according to Bessman (Bessman and Geiger, 1981 ; Bessman and Carpenter, 1985)], requires CK to be at sites of energy production and energy consumption. We know that the mitochondrial CK reaction is driven by the translocase running unidirec-tionally producing PCr (Saks et al., 1978; Jacobus, 1985; Wallimann et al.,

1992). In myofibrils it is driven in the forward direction only by the steady state rate of myosin ATPase in the direction of PCr utilization (Clark et al., 1995). This is a kinetically favourable reaction and close spatial localization of these two proteins within the same cellular compartment makes their interaction very efficient (Ventura-Clapier et al., 1987a,b; Hoerter and Ventura-Clapier,

1993). Exactly the same is true for subcellular membranes such as the sarcoplasmic reticulum and the sarcolemma (Saks et al., 1978). In the cytoplasmic compartment CK operates at equilibrium (Meyer et al., 1984; Bessman and Carpenter, 1985; Jacobus, 1985; Kushmerick et al., 1992; Wegmann et al., 1992; Wyss et al., 1992; Aliev and Saks, 1993; see also Chapter 6). However, this equilibrium reaction may occur in a highly structured medium within the cytoplasm. This may be necessary because several components of the reaction (adenine nucleotides and associated energetic enzymes) exist in multiple microcompartments and so concentration gradients may exist (for review, see Glegg, 1984; Yee and Jones, 1985; Jones, 1986; Wallimann et al., 1992). We may assume, however that the total reaction is at equilibrium throughout the cytoplasm as a result of multiple equilibrium states of cellular PCr-creatine with ATP-ADP pools.

In the cytoplasm, CK concentration (activity) is high (Ventura-Clapier et al., 1987b) and the enzyme may be involved in complexes with other cytoplasmic proteins (Dillon and Clark, 1990; Clark et al., 1995) (cytoskeleton, direction of metabolic wove propagation -

direction of metabolic wove propagation -

myofibrillar space

^ - porin channel; (^^-myofibrillar CK; ^ - turnover number of CK; VrK

VATP ^phosphorylation.

myofibrillar space

^ - porin channel; (^^-myofibrillar CK; ^ - turnover number of CK; VrK

VATP ^phosphorylation.

Figure 5.6 Consecutive ADP and creatine concentration changes in microcompart-ments associated with cytoplasmic CK result in a shift from equilibrium. This is induced by cyclic ADP liberation during contraction. The result is a wave-like feedback acting as a signal from myofibrils to mitochondria. For further explanation, see the text. CK myo, myofibrillar CK; CK (enclosed in triangle), cytoplasmic CK; Kck/Fatp =5-50; v, turnover number of CK; t= 1/k n, number of cycles of rephosphorylation.

glycolytic enzymes, etc.), leading to the formation of dynamic microcompart-ments for ATP or ADP in the cytoplasmic space between two neighbouring CK molecules. The proposed PCr concentration changes induced by ADP production during the contraction cycle in myofibrils are illustrated (Fig. 5.6). In agreement with, and in addition to, the concept of Nagle (Nagle, 1970a; Koretsky et al., 1985), this figure shows that within the myofibrillar space local ADP increases could be quickly replaced by a change in creatine concentration due to ADP rephosphorylation at the expense of PCr via the coupled CK reaction - this is the first step for signal transformation (Ventura-Clapier et al., 1987a,b; Hoerter et al., 1993). The next steps are sequential local cyclic changes of ADP and creatine concentrations due to phosphoryl group transfer by cytoplasmic CK (facilitated diffusion, or vectorial ligand conduction; Meyer et al., 1984). Since each step brings the previous one back into equilibrium and quenches the deviation from equilibrium at that step, a single metabolic stimulus alone - alternating local changes in ADP and creatine concentrations - would propagate from myofibrils to mitochondria. The frequency of this signal is that of contraction (heart rate), but the amplitude may decrease in the direction of the stimulus wave owing to high creatine and creatine phosphate mobility (Nagle, 1970a,b). The amplitude may also be a function of the energetic demands. In cardiomyocytes, the sarcomere contractions are synchronized and the stimuli described are distributed in all directions to all mitochondrial populations. On reaching the mitochondria, the local change in creatine concentration would stimulate the reactions leading to rephosphorylation. If the mitochondria receive a signal as a local ADP concentration change, then this signal is amplified by the coupled mitochondrial CK enzyme system. This would induce rapid PCr production and signal quenching. The result would represent a rapid and effective response to energetic demand.

It is very important that metabolic signal transduction occurs with a rate exceeding the rate of ATP turnover by an order of magnitude (Koretsky et al., 1985; Jeremy et al., 1993). The use of NMR magnetization transfer has given values for the rate of cardiac ATP synthesis (phosphate-ATP transfer) in vivo which range from 1-3 fxmol/g dry weight/s, depending upon the workload (Nunnally and Hollis, 1979; Zahler et al., 1987; Zahler and Ingwall, 1992; Jeremy et al., 1993). This rate is close to the rate of ATP synthesis calculated from rates of oxygen uptake in isolated mitochondria (Jeremy et al., 1993). The net rate of the CK reaction (ATP-PCr or PCr ATP transfer) is, however 20-30 /¿mol/g dry weight/s (Nunnally and Hollis, 1979; Zahler et al., 1987; Zahler and Ingwall, 1992; Jeremy etal., 1993). Because magnetization transfer experiments are not able to distinguish between subcellular populations, the above results include the rates of the unidirectional mitochondrial or myofibri-lar flux (Zahler and Ingwall, 1992), and cytoplasmic equilibrium CK reactions which have a value of about 20-25 ¿unol/g dry weight/s. In the ("simple") mathematical analysis of facilitated diffusion of ATP and PCr in cells, Meyer et al. showed that with CK at or near equilibrium, the PCr flux is dominant, representing more than 99% of high-energy phosphate flux (Kushmerick et al., 1992). From this observation, we can conclude that the equilibrium of CK is required for rapid signal transduction between two (or more) functionally coupled CK systems in myofibrils (and at membranes) and in mitochondria, respectively.

Concerning the feedback signal transduction, it is possible that there is another similar system functioning in the muscle cells - the adenylate kinase system. Against the background of a high ATP concentration this reaction (2ADP^ATP+AMP) may contribute to the feedback signal which reaches mitochondria as local changes in ADP concentration (Zelenznikar et al., 1990). However, because of the low permeability of the mitochondrial outer membrane for ADP, creatine is needed for signal amplification and for myocardial PCr production. This new concept is considered further by Saks et al. (1995).

REFERENCES

Aliev, M.K. and Saks, V.A. (1993). Quantitative analysis of the "phosphocreatine shuttle": I. A probability approach to the description of phosphocreatine production in the coupled creatine kinase-ATP/AD"P" translocase - oxidative phosphorylation reactions in heart mitochondria. Biochem. Biophys. Acta 1143, 291-300.

Balaban, R.S. (1990). Regulation of mitochondrial oxidative phosphorylation in mammalian cells. Am. J. Physiol. 258, C377-389.

Balaban, R.S., Kantor, H.L., Katz, L.A. and Briggs, R.W. (1986). Relation between work and phosphate metabolites in the in vivo paced mammalian heart. Science 232,1121-1123.

Benz, R., Kottke, M. and Brdiczka, D. (1990). The cationically selective state of the mitochondrial outer membrane pore: a study with intact mitochondria and reconstituted mitochondrial porin. Biochem. Biophys. Acta 1022, 311-318.

Bessman, S.P. and Carpenter, C.L. (1985). The creatine-creatine phosphate energy shuttle. Ann. Rev. Biochem. 54, 831-862.

Bessman, S.P. and Geiger, P.J. (1981). Transport of energy in muscle. The phosphorylcreatine shuttle. Science 211,448^152.

Brdiczka, D. (1991). Contact sites between mitochondrial envelope membranes - structure and function in energy-transfer and protein-transfer. Biochem. Biophys. Acta 1071,291-321.

Chance, B. and Williams, G.R. (1955). Respiratory enzymes in oxidative phosphorylation. III. The steady state. J. Biol. Chem. Ill, 409^127.

Chance, B. and Williams, G.R. (1956). The respiratory chain and oxidative phosphorylation. Adv. Enzymol. 17,65-134.

Clark, J.F., Kemp, G.J. and Radda, G.K. (1995). The creatine kinase equilibrium, free [ADP] and myosin ATPase in vascular smooth muscle cross-bridges. J. Theor. Biol. 173,207-211.

Colombini, M. (1987). Regulation of the mitochondrial outer membrane channel, VADC. J. Bioenerg. Biomembr. 19, 305-358.

de Pinto, V., Ludwig, O., Krause, J., Benz, R. and Palmieri, F. (1987). Porin pores of mitochondrial outer membranes from high and low eukaryote cells: biochemical and biophysical characterization. Biochem. Biophys. Acta. 894,109-119.

Dillon, P.F. and Clark, J.F. (1990). The theory of diazymes and functional coupling of pyruvate kinase and creatine kinase. J. Theor. Biol. 143,275-284.

Glegg, J. (1984). Properties and metabolism of the aqueous cytoplasm and its boundaries. Am. J. Physiol. 246, R133-R151.

Hansford, R.G. (1985). Relation between mitochondrial calcium transport and control of energy metabolism. Rev. Physiol. Biochem. Pharmacol. 102,2-72.

Heineman, F.W. and Balaban, R.S. (1990). Control of mitochondrial respiration in the heart in vivo. Ann. Rev. Physiol. 52, 523-542.

Hoerter, J.A. and Ventura-Clapier, R. (1993). Modulation of cardiac mammalian contractility by high energy phosphate depletion and creatine kinase activity. In: Mechanisms of Control and Adaptation (Hichachka, P.W., Lutz, P.L., Sick, T., Rosenthal, M. and Van den Thillart, G.) pp. 311-327. CRC Press, London.

Jacobus, W.E. (1985). Respiratory control and integration of heart high energy phosphate metabolism by mitochondrial creatine kinase. Ann. Rev. Physiol. 47,707-725.

Jeremy, R.W., Ambrosio, G., Pike, M.M., Jacobus, W.E. and Becker, L.C. (1993). The functional recovery of post-ischemic myocardium requires glycolsis during early reperfusion. J. Mol. Cell. Cardiol. 25,261-276.

Jones, D.P. (1986). Intracellular diffusion gradients of Oz and ATP. Am. J. Physiol. 250, C663-C675.

Katz, L.A., Koretsky, A.P. and Balaban, R.S. (1987). Respiratory control in the glucose perfused heart. A P-NMR and NADH fluorescence study. FEBS Lett. 221,270-276.

Katz, L.A., Swain, J.A., Portman, M.A. and Balaban, R.S. (1989). Relation between phosphate metabolites and oxygen consumption of heart in vivo. Am. J. Physiol. 256, H265-H274.

Kayser, H„ Kratzin, D., Thinnes, F.P., Götz, H., Schmidt, W.E., Eckrart, K. and Hilschmann, N. (1988). Characterization and primary structure of a 31 kD porin. Biol. Chem. Hoppe - Seyler 370,1265-1278.

Koretsky, A.P., Basus, V.J., James, T.L., Klein, M.P. and Weiner, M.V. (1985). Detection of exchange reactions involving small metabolite pools using NMR magnetization transfer techniques: relevance to subcellular compartmentation of creatine kinase. Magn. Reson. Med. 2, 586-594.

Kottke, M., Adam, V., Riesinger, I., Bremm, G., Bosch, W., Brdiczka, D., Sandri, G. and Panfili, E. (1988). Mitochondrial boundary membrane contact sites in brain: points of hexokinase and creatine kinase location and control of Ca2+ transport. Biochem. Biophys. Acta 935,87-102.

Kushmerick, M., Meyer, R.A. and Brown, T.R. (1992). Regulation of oxygen consumption in fast and slow-twich muscle. Am. J. Physiol. 263, C598-C606.

Kuznetsov, A.V., Khuchua, Z.A., Vasileva, E.V., Medvedeva, N.V. and Saks, V.A. (1989). Heart mitochondrial creatine kinase revisited: outer mitochondrial membrane is not important for coupling of phosphocreatine production to oxidative phosphorylation. Arch. Biochem. Biophys. 268,176-190.

Liu, M. and Colombini, M. (1991). Voltage gating of the mitochondrial outer membrane channel VDAC is regulated by a very conservative protein. Am. J. Physiol. 260, C371-C374.

Mannella, C.A. and Tedeschi, H. (1987). Mini-Review. Importance of the mitochondrial outer membrane channel as a model biological channel. J. Bioenerg. Biomembr. 19, 305-308.

McKormac, J.C., Halestrup, A.P. and Denton, R.M. (1990). Role of calcium ions in regulation of mammalian intramitochondrial metabolism. Physiol. Rev. 70,391-425.

Meyer, R.A., Sweeney, H.L. and Kushmerick, M.L. (1984). A simple analysis of the "phosphocreatine shuttle" Am. J. Physiol. 246, C365-C377.

Nagle, S. (1970a). Die Bedeutung von kreatinphosphat and adenosintriphosphat im hinblick auf energiebereitstellung, -transport und Verwertung im normalen und insuffizienten herzmuskel. Klin. Wschr. 48,332-339.

Nagle, S. ( 1970b). Regelprobleme imenergiestoffwechseldes hermuskles. Klin Wschr.48,1075-1089.

Nunnally, R.L. and Hollis, D.P. (1979). ATP compartmentation in living hearts: a phosphorus nuclear magnetic resonance saturation transfer study. Biochemistry 18,3642-3647.

Saks, V.A., Rosenshtraukh, L.V., Smirnov, V.N. and Chazov, E.I. (1978). Role of creatine Phosphokinase in cellular function and metabolism. Can. J. Physiol. Pharmacol. 56,691-706.

Saks, V.A., Belikova, Y.O., Kuznetsov, A.V., Khuchua, Z.A., Branishte, T.H., Semenovsky, M.L. and Naumov, V.G. (1991a). Phosphocreatine pathway for energy transport: ADP diffusion and cardiomyopathy. Am. J. Physiol. Suppl. 261,30-38.

Saks, V.A., Belikova, Yu.O. and Kuznetsov, A.V. (1991b). In vivo regulation of mitochondrial respiration in cardiomyocytes: specific restrictions for intracellular diffusion of ADP. Biochem. Biophys. Acta 1074, 302-311.

Saks, V.A., Vasil'eva, E., Belikova, Yu. O., Kuznetsov, A.V., Lyapina, S. and Petrova, L. and Perov, N.A. (1993). Retarded diffusion of ADP in cardiomyocytes: possible role of mitochondrial outer membrane and creatine kinase in cellular regulation of oxidative phosphorylation. Biochem. Biophys. Acta 1144,134-148.

Saks, V.A., Kuznetsov, A.V., Khuchua, Z.A., Vasilyeva, E.V., Belikova, Yu.O., T. Kesvatera and T. Tiivel. (1995). Control of Cellular Respiration in vivo by mitochondrial outer membrane and by creatine kinase. A new speculative hypothesis: possible involvement of mitochondrial cytoskeleton interactions. J. Mol. Cell. Biochem. 27,625-645.

Sjostrand, F.S. (1978). The structure of mitochondrial membranes: a new concept. J. Ultrastruct. Res. 64,217-245.

Stoner, C.D. and Sirak, H.D. (1969). Osmotically-induced alterations in volume and ultrastructure of mitochondria isolated from rat liver and bovine heart. J. Cell Biol., 43,521-538.

Tedeschi, H. and Kinnally, W. (1987). Mini-review. Channels in the mitochondrial outer membrane: evidence from patch clamp studies. J. Bioenerg. Biomembr. 19, 321-327.

Unitt, J.F., Schräder, J., Brunotte, F., Radda, G.K. and Seymour, A.M.L. (1992). Determination of free creatine and phosphocreatine concentrations in the isolated rat heart. Biochem. Biophys. Acta 1133, 115-120.

Veech, R.L., Lawson, J.W.R., Cornell, N.W. and Krebs, H.A. (1979). Cytosolic phosphorylation potential. J. Biol. Chem. 254,6538-6547.

Ventura-Clapier, R., Mekhfi, H. and Vassort, G. (1987a). Role of creatine kinase in force development in chemically skinned rat cardiac muscle. J. Gen. Physiol. 89,815-837.

Ventura-Clapier, R., Saks, V.A., Vassort, G., Lauer, C. and Elizarova, G.V. (1987b). Reversible MM-creatine kinase binding to cardiac myofibrils. Am. J. Physiol. 253, C444-C445.

Wallimann, T., Wyss, M., Brdiczka, D. and Nicolay, K. (1992). Intracellular compartmentation, structure and function of creatine kinase isoenzymes in tissues with high and fluctuating energy demands: the "phosphocreatine circuit" for cellular energy homeostasis. Biochem. J. 281, 21—40.

Wegmann, G., Zanolla, E., Eppenberger, H.M. and Wallimann, T. (1992). In situ compartmentation of creatine kinase in intact sarcomeric muscle: the acto-myosin overlap zone as a molecular sieve. J. Muscle Res. Cell Motil. 13,420-435.

Wyss, M., Smeitink, J., Wevers, R.A. and Wallimann, T. (1992). Mitochondrial creatine kinase: a key enzyme of aerobic energy metabolism. Biochem. Biophys. Acta 1102,119-166.

Yee, T. and Jones, D.P. (1985). ATP concentration gradients in cytosol of liver cells during hypoxia. Am. J. Physiol. 249, C385-C392.

Zahler, R. and Ingwall, J.S. (1992). Estimation of heart mitochondrial creatine kinase flux using magnetization transfer NMR spectroscopy. Am. J. Physiol. 262, H1022-H1028.

Zahler, R., Bittl, J.A. and Ingwall, J. (1987). Analysis of compartmentation of ATP in skeletal and cardiac muscle using 3,P nuclear magnetic resonance saturation transfer. Biophys. J. 51, 883-893.

Zeleznikar, R.J., Heyman, R.A., GraefT, R.M., Walseth, T.F., Dawis, S.M., Butz, E.A. and Goldberg, N.D. (1990). Evidence for compartmentalized adenylate kinase catalysis serving a high energy phosphoryl transfer function in rat skeletal muscle. J. Biol. Chem. 265,300-311.

Zimmerberg, J. and Parsegian, V.A. (1987). Mini-review. Water movement during channel opening and closing. J. Bioenerg. Biomembr. 19,351-358.

Was this article helpful?

0 0
Turbo Metabolism

Turbo Metabolism

Forget Silly Diets-They Don't Work. Weight loss has got to be the most frustrating experience for many people, young and old alike. Eating foods that are just horrible, denying yourself foods you truly love and enjoy. Exercising, even though you absolutely hate exercising, and end up stiff as a board with no results.

Get My Free Ebook


Post a comment