Effect of noradrenaline on rest-dependent and excitation-dependent exchange of calcium in the ventricular muscle of guinea-pig heart

Abstract

The effect of noradrenaline (NA) on the "contractile calcium" was investigated in the ventricular muscle of guinea-pig heart. It was found that NA in doses increasing the steady-state contractile force by 50-100% increased the beat-to-beat exchange of 45Ca (Ca1 fraction) by about 50%, and significantly increased Ca2 fraction which is lost from the cells at rest and re-accumulated during subsequent stimulation. It has been proposed elsewhere that this fraction may control the force of contractile response to the triggering Ca1 fraction. It is concluded that NA increases beat-to-beat Ca exchange and affects intracellular Ca distribution.