[Regulation of the heart mitochondrial respiration rate. Comparison of oxidation of succinate and NAD-dependent substrates]. / Reguliatsiia skorosti dykhaniia v mitokhondriiiakh serdtsa. Sravnenie okisleniia suktsinata i NAD-zavisimykh substratov.

Regulation of respiration at all rates between State 4 and State 3 was studied in heart mitochondria oxidizing FAD- and NAD-dependent substrates (succinate, pyruvate + + malate and palmitoylcarnitine). The creatine phosphokinase ADP-regenerating system was used which allows to fix the concentrations of extramitochondrial adenine nucleotides in such a way that the rate of respiration is controlled by mitochondrial processes alone. It was shown that respiration is controlled by delta mu(H+)-utilizing system within the respiration rate interval from State 4 till 70-80% of the maximal rate in State 3 (corresponding to physiological rates) both for NAD- and FAD-dependent substrates. The main step in the control of respiration near State 4 is proton leakage through the inner mitochondrial membrane, whereas in all the other parts of the mentioned interval this role is assigned to the adenine nucleotide translocator (ANT). The control coefficient for ANT is higher, while that of proton leakage is lower at the same relative rates of respiration with NAD-dependent substrates compared with succinate. These differences were found to be related to much higher values of the membrane potential generated at the same relative rates of succinate oxidation in comparison with the case with pyruvate + + malate. The contribution of delta mu(H+)-utilizing system to respiration control sharply decreases, whereas that of the delta mu(H+)-generating system increases at maximal rates of respiration near State 3. This phenomenon in more characteristic of succinate. In this case the control coefficient of ANT drops to zero, while that of succinate dehydrogenase rises to 0.7.

[The role of long-chain acyl-CoA in the disturbances of oxidative phosphorylation in the myocardium]. / Rol' dlinnotsepochechnykh atsil-KoA v narushenii okislitel'nogo fosforilirovaniia v miokarde.

The effect of intramitochondrial acyl-CoA on the respiration of rabbit heart mitochondria in different metabolic states was studied. Acyl-CoA inhibited O2 consumption by 11% in State 4 and by 6% in State 3. However, the effect of acyl-CoA was more pronounced (20%) in the intermediate state of respiration between State 4 and State 3. The data obtained suggest that acyl-CoA can regulate oxidative phosphorylation in heart mitochondria in vivo.

[The role of adenine nucleotide translocator in the regulation of oxidative phosphorylation in heart mitochondria]. / Rol' perenoschika adeninnukleotidov v reguliatsii okislitel'nogo fosforilirovaniia v mitokhondriiakh serdtsa.

The regulatory role of adenine nucleotide translocase in oxidative phosphorylation was determined by titration of respiration of isolated rabbit heart mitochondria with carboxyatractyloside in the creatine phosphokinase ADP-regenerating system, which is not rate-limiting. It was found that the respiration rate is not controlled by adenine nucleotide translocase in states 3 and 4. Within the physiological region of respiration (30-70% of the maximal rate), the control coefficient for ADP/ATP translocase is 0.62-0.75. Thus, translocase plays a key role in the regulation of oxidative phosphorylation.

[Participation of the adenine nucleotide translocator in the regulation of pyruvate oxidation in heart mitochondria]. / Uchastie perenoschika adeninnukleotidov v reguliatsii okisleniia piruvata v mitokhondriiakh serdtsa.

A regulatory role of adenine nucleotide translocator (ANT) was determined by titration of mitochondrial respiration (state 3) with carboxyatractyloside. It was shown that ANT regulates pyruvate oxidation: the control strength is more pronounced after depletion of endogenous substrates or after the increase in extramitochondrial ATP/ADP. The rate of succinate oxidation is controlled mainly by succinate dehydrogenase, while ANT does not participate in its regulation.

[Effect of ischemia and rotenone on lipid and adenine nucleotide levels and functional activity of heart mitochondria]. / Vliianie ishemii i rotenona na soderzhanie lipidov, adeninnukleotidov i funktsional'nuiu aktivnost' mitokhondrii serdtsa.

Myocardial mitochondria (MCh), isolated with rotenone (MCh + RO) and in absence of rotenone (MCh - RO), were studied in rabbits with ischemia (0.5 hr autolysis) and in controls. Content of acyl-CoA was increased by 50%, linoleic acid - by 49% and lysophosphatidyl choline - by 37% in MCh + RO of control animals as compared with the MCh - RO preparation. In the MCh + RO preparation from rabbits with ischemia content of acyl-CoA was increased by 62%, while concentration of free fatty acids (FFA) and phospholipids was similar to those of the MCh - RO preparation. After isolation of mitochondria with rotenone composition of adenine nucleotides was distinctly altered. Content of ATP was decreased by 27% in mitochondria of both ischemic and control animals, although total amount of adenine nucleotides was decreased only slightly. As shown by estimation of succinate oxidation and membrane potential rotenone did not affect the mitochondrial respiration. In mitochondria of ischemic rabbits concentrations of FFA and lysophosphatidyl choline were increased, whereas content of ATP, total amount of adenine nucleotides, the rate of succinate oxidation and membrane potential were decreased. The method developed, isolation of mitochondria with rotenone, may be used in studies of the role of acyl-CoA in energy metabolism of cells.

[Kinetic differences in the oxidative phosphorylation system of control and ischemia-damaged heart mitochondria]. / O kineticheskikh razlichiiakh sistemy okislitel'nogo fosforilirovaniia kontrol'nykh i povrezhdennykh ishemiei mitokhondrii serdtsa.

Rabbit heart mitochondria isolated with or without rotenone (M + R and M -R, respectively) were studied. It was shown with the use of pHmetry that the Vmax of oxidative phosphorylation decreased during ischemia (autolysis for 0.5 h at 37 degrees C) in both preparations of the mitochondria to the same extent. The Km for ADP was unchanged in M - R, but rose significantly in M + R. Carnitine reduced the ischemia -increased Km value. The data suggest the inhibition of adenine nucleotide translocase by longchain acyl-Co A, whose level was found to be elevated by 52% in M + R during ischemia.