EFFECTS OF EPINEPHRINES ON METABOLISM AND CONTRACTION OF CAT PAPILLARY MUSCLE.

Abstract

The change of metabolic state and contractility of heart induced by epinephrine and norepinephrine was studied in in vitro preparations of cat papillary muscle. The oxygen consumption, glycogen content, energy-rich phosphate content, and contractility of muscles were measured simultaneously whenever possible by techniques described previously. It was found that these amines did not change significantly the tissue contents of energy-rich phosphate compounds and glycogen in these conditions. The oxygen consumption and contractility of muscles were markedly influenced by the sympathomimetic amines. The change of metabolic efficiency as measured by the ratio, contractile tension : total Qo2, following the administration of these amines were dependent on the condition of heart muscles at the time of administration of these agents. Thus, when muscles were fresh, the metabolic efficiency was not significantly changed by the amines. However, when muscles were in the hypodynamic state, the amines were found to increase the metabolic efficiency of the heart muscle significantly. This suggests that the metabolic state of heart muscle should be taken into consideration whenever the influence of these sympathomimetic amines on the mechanical efficiency of heart is investigated.