An endogenous ‘hypertensive factor’ enhances the voltage‐dependent calcium current

Abstract

The effects of an immunoaffinity-purified putative endogenous hypertensive factor (HF) on voltage-dependent calcium current in frog cardiac myocytes were assessed. In 9 out of 10 cells, HF reversibly increased the peak amplitude of the calcium current. HF increased peak calcium current density at -5 mV from a control level of 1.8 & 1.3 pA/pF (mean & SD) to 4.4 + 2.0 pA/pF. HF shifted the peak of the calcium current-voltage relationship in the hyperpolarizing direction. HF shifted the voltage dependence of the inactivation of the calcium current to more negative potentials with prepulses from 40 to 0 mV, but the inactivation was not affected with prepulses more positive than 0 mV. Modulation of the voltagedependent calcium current by HF may be the mechanism underlying its pressor effects.