Effect of epinephrine on stress relaxation and distensibility of the isolated cat heart

Abstract

To investigate the cause of the rapid relaxation observed in the epinephrine-stimulated heart, stress relaxation and distensibility have been measured in the isolated perfused cat heart and in isolated papillary muscles. During epinephrine stimulation, distensibility was slightly increased but there was no change in the rate of stress relaxation. This would suggest that the action of epinephrine is confined to the contractile elements without any direct effect on the viscoelastic elements responsible for stress relaxation. The rapid diastolic relaxation observed in these hearts therefore relates to the dynamics of the contraction process rather than to lowered myocardial viscosity.