Oxidative Activity of Aortic Tissue of Man, the Rabbit and the Dog, With Special Reference to Succinic Dehydrogenase and Cytochrome Oxidase

Abstract

Succinic dehydrogenase and cytochrome oxidase activities were determined in homogenates of three aortic segments (ascending and arch, descending thoracic, abdominal) and liver of man, the rabbit and the dog. Both enzymes exhibited the lowest activity in human aorta. Succinic dehydrogenase exhibited the highest activity in the thoracic aorta of the dog and intermediate activity in the latter''s abdominal segment and the rabbit''s aorta. Cytochrome oxidase, in contrast, exhibited the highest activity in the rabbit''s aorta. A slight gradient of decreasing activity from thoracic to abdominal aorta was noted for cytochrome oxidase in both the rabbit and dog and for succinic dehydrogenase in the rabbit, whereas a significant decrease in the latter enzyme was noted in the abdominal segment of the dog. No gradient of activity was apparent in man. Liver exhibited the lowest activity for both enzymes in man, highest in the dog and intermediate in the rabbit. The above findings suggest a biologic species difference between the aorta of man, the rabbit and the dog, which may be partly ascribed to a difference in the components of the above two enzymatic systems. The same species difference holds true for hepatic tissue.