Abstract
The oxidative phosphorylation of liver mitochondria in old-aged rats or human is supposed to be injured since the mitochondria were found to be fewer in number and larger in volume than those in younger rats or human. However, recent study showed that the efficiency of oxidative phosphorylation of liver mitochondria in old-aged rats is the same as that of liver mitochondria in younger rats. There is still some possibility that the mitochondria in old group is injured much more easily than that in younger group under certain conditions. In this report, we demonstrated that ADP/O and RCR of liver mitochondria in old-aged rats were decreased much more than those of liver mitochondria in younger rats when the mitochondria were left at room temperature for 30 minutes or were prepared from rats in which tolbutamide, one of uncouplers, had been given orally. Further more, due to addition of 0.2mM Ca++ in vitro the decrease in ADP/O and RCR of the mitochondria in old-aged rats was decreased much more than those of the mitochondria in younger rats when mitochondria were prepared from rats with tolbutamide loading. These results suggest that the liver mitochondria in old-aged rats become very sensitive to various stresses.
