[Respiratory function of mitochondria in the inner and outer layers of the dog myocardium]

The respiratory effect of dog myocardial mitochondria was studied by measuring oxygen content in a reaction chamber using Garbani electrode. 1) In normal dog mitochondria, oxygen consumption rate (QO2) in state 3 and state 4, respiratory control ratio (RCR) and ADP/O ratio were not different between the inner and outer layers when glutamate or succinate was used as substrate. 2) Thirty min after the occlusion of one of the small branches of the anterior descending artery, there were no differences in the respiratory effects between the inner and outer layers when glutamate or succinate was used as substrate. HOowever, compared with the normal dog mitochondria, ADP/O ratio, QO2 in state 3 and state 4 were lower in the outer layer and QO2 in state 4 was lower in the inner layer when succinate was used as substrate. 3) When the anterior descending branch was narrowed to decrease the blood flow to about a half, the respiratory effects were not different between the inner and outer layers when succinate was used as substrate. However, ADP/O ratio in the outer layer was lower than that of the normal dog. 4) Nitroglycerin had no effect on the respiratory effects either in vitro (1.63 X 10(-6) M, succinate as substrate) or in vivo (20 mug/kg i.v., glutamate as substrate.) 5) Dipyridamole had no effect on the respiratory effects in vivo (250 mug/kg, i.v., glutamate as substrate) but, ADP/O ratio in the outer layer was diminished in vitro (7.34 X 10(-6) M, succinate as substrate).