Histochemistry of the myocardium and its vasculature in the normal rat

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Abstract
Coronary arteries and arterioles in the left and right normal rat ventricle were examined histochemically to determine their metabolic activities. Aerobic metabolic capacity was determined by assessing the reactivities of the enzymes succinate dehydrogenase, cytochrome oxidase and myosin ATPase. Glucose-6-phosphate dehydrogenase was examined to determine the activity of the hexose-monophosphate-shunt, while lactate dehydrogenase and glycogen reactivity were determined as an evaluation of the anaerobic metabolic capacity. The amounts of deoxyribonucleic and ribonucleic acid were assessed as an indication of protein synthesis. Reactivities of the enzymes succinate dehydrogenase, cytochrome oxidase and myosin ATPase are greater in arteriolar smooth muscle than in arteries. This suggests that arterioles have a higher capacity for aerobic metabolism than do arteries. The greater reactivity for lactate dehydrogenase and glycogen in arterial smooth muscle than in arterioles suggests that arteries are more adapted for anaerobic metabolism. Glucose-6-phosphate dehydrogenase shows substantially greater activity in arteries and in some larger arterioles than in most smaller coronary arterioles, which implies that the coronary arteries and larger arterioles possess a higher capacity for nucleic acid and protein synthesis. Deoxyribonucleic and ribonucleic acids show low reactivity in both arteries and arterioles from the ventricular myocardium, which conforms to the view that under normal conditions, the coronary vasculature is stable with little cell proliferation.