Relationship between structure and fatty acid metabolism in mitochondria isolated from ischemic rat hearts

We studied mitochondrial structure and intermediates of fatty acid metabolism in mitochondria isolated from ischemic hearts. By electron microscopy, no structural difference was detected between mitochondria isolated from control hearts and from ischemic hearts receiving glucose as the only substrate. However, major differences were observed in mitochondria obtained from control and ischemic hearts receiving both glucose and palmitate. These hearts contained a higher portion of damaged mitochondria. However, measurements of marker enzyme activities failed to show that more mitochondria were lost during the isolation procedure in ischemic than in control hearts. Many densely staining areas (or amorphous densities) were observed in the isolated mitochondria of ischemic hearts. These amorphous densities have an appearance similar to that observed in the intact ischemic heart under the same perfusion conditions. Levels of long-chain acyl-CoA in mitochondria isolated from hearts receiving glucose alone were practically the same for control and ischemic hearts and were only slightly increased in mitochondria of ischemic hearts receiving both glucose and palmitate. On the other hand, levels of long-chain acyl carnitine in mitochondria of ischemic hearts were twice those found in control hearts. The mitochondrial level of long-chain acyl carnitine was approximately four times higher in the ischemic hearts receiving palmitate compared to those receiving no palmitate. This rise in long-chain acyl carnitine levels in mitochondria isolated fom ischemic hearts receiving palmitate may be related to modifications of the mitochondrial structure and to the appearance of amorphous densities.