Ribonucleic acid (RNA) polymerase and adenyl cyclase in cardiac hypertrophy and cardiomyopathy

Abstract

The key enzyme in the genetic process of protein synthesis, ribonucleic acid (RNA) polymerase, is increased in activity during the early stages of cardiac hypertrophy induced by aortic banding. A similar increase in the activity of this enzyme is seen in the cardiomyopathy of the Syrian golden hamster. There are at least two RNA polymerases in the cell. RNA polymerase I is nucleolar in origin and synthesizes ribosomal RNA under conditions of reduced ionic strength. RNA polymerase II is nucleoplasmic in location and chiefly synthesizes deoxyribonucleic acid (DNA)-like RNA or messenger RNA. The latter enzyme is strongly inhibited by alpha amanitine, a toxic cyclopeptide obtained from the common poisonous mushroom. Increased adenyl cyclase activity in the myocardium of the hamster with cardiomyopathy suggests that catecholamines and cyclic adenosine monophosphate may play an important role in the pathogenesis of the condition.