European Journal of Biomedical and Pharmaceutical Sciences

COUPLED AND NONCOUPLED RESPIRATION IN RAT CARDIOCYTES AND MITOCHONDRIA

R.N. Akhmerov*, B. A. Niyazmetov, S. O. Mirzakulov, D. Sh. Hamdamov and K. T. Almatov

ABSTRACT

The respiration of rat cardiocyties while oxidizing different substrates was studied polarographically to quantify rates of coupled and noncoupled respiration at 370C in incubation medium. Cardiocyte respiration rates were higher in state-4 with succinate than with NAD-linked substrates especially being used high substrate concentration. The rate of the oxygen consumption in intact cardiocytes did not change after addition of NADH and ADP. In the presence of digitonin cаusing increase of cytoplasmic membrane permeable. ADP increased cardiocyte respiration rate approximately three-fold with pyruvate (+ malate) as substrate and less than two-fold with succinate as substrate. In presence of digitonin (30 ng/ml and cytochrome c (2 mg/ml), the cells oxidized exogenous NADH (1 mM) at a high rate that did not change after addition of ADP. Rotenone blocked the oxidation of exogenous NADH. In the presence of digitonin and cytochrome c (2 mg/ml), ascorbate (20 mM) was also oxidized at a high rate which did not change after ADP addition. Oligomycin, which blocks the ATP synthase, did not decrease the rate of succinate oxidation in state-4 and NADH or ascorbate oxidation. Mitochondria isolated from collagenase treated hearts responded similarly to the different substrates and inhibitors as did the cardiocytes. Based on these findings, it appears that cardiocytes are able to oxidize substrates by two pathways, one coupled to the synthesis of ATP (coupled respiration) and one not inhibited by oligomycin and thus not connected with synthesis of ATP (noncoupled respiration).

Keywords: Cardiocytes, mitochondria, NAD-linked substrates, succinate, NADH, ascorbate, cytochrome c, coupled and noncoupled respiration.