Inhibitory action of mibefradil on T-type calcium channels in early embryonic mouse ventricular myocytes

Abstract

Mibefradil has been reported to preferentially block T-type Ca(2+) channel currents in many different tissues including heart with variable potencies. T-type Ca(2+) currents (I(sub Ca-T)) in early embryonic (9.5 day post coitum (dpc)) mouse ventricular myocytes were recorded using a whole-cell patch clamp method and the effects of mibefradil were studied. I(sub Ca-T) were inhibited by mibefradil in a concentration-dependent manner with half inhibitory concentration (IC(sub 50)) at 3.4 +/- 0.2 micro-M. This value is higher than those reported for native adult and neonatal atrial myocytes (0.1-1.5 micro-M). Factors affecting the mibefradil sensitivity of I(sub Ca-T) in particular different subtypes of alpha1 subunits, are discussed.