[The effect of carbocromen on the respiratory function of rat heart mitochondria]

Rat heart mitochondria were isolated by a slightly modified method of Sordahl. The influence of carbocromen (Intensaín) on the respiratory function of the tightly coupled or uncoupled mitochondria was tested in the presence of the respiratory substrates pyruvate, alpha-ketoglutarate, D,L-palmitoylcarnitine, L-palmitoylcarnitine, and D,L-acetylcarnitine. Carbocromen (0.089--0.89 mmol/l) did not change the P/O ratio, but reduced the rate of oxygen consumption (QO2) of the coupled mitochondria by about 20% when palmitoylcarnitine was used as respiratory substrate. With ADP in excess (5 mmol/l) carbocromen decreased QO2 in state ST3 by about 35%. This drug induced reduction of QO2 is still much more evident in uncoupled mitochondria (18% with 0.045 mmol/l carbocromen, 70% with 0.89 mmol/l carbocromen). In the presence of pyruvate as substrate the respiratory function of the coupled and uncoupled mitochondria remained nearly unchanged after adding the drug. It is discussed that carbocromen could interact with the complex enzyme dependent transport of long-chain fatty acids through the mitochondrial membrane.