Nisoldipine: a new, more selective calcium current blocker in cardiac Purkinje fibers.

Nisoldipine is a new dihydropyridine derivative which is structurally related to the calcium current blocker nifedipine. In this paper, the effects of this new blocker are studied on Purkinje fiber plateau currents and are compared with the effects of D600 on the same currents. The results show that, like D600, at concentrations near 10 microM nisoldipine can completely block the slow inward current and contractile activation. As is the case for D600, at these concentrations, nisoldipine reduces the transient outward current. However, in contrast to D600 and other calcium current blockers, this new compound does not reduce the delayed rectifier. In addition, these experiments indicate that the block of slow inward current by nisoldipine is much less sensitive to membrane potential than is the case for the block by D600 of this current. These results show that nisoldipine is a more selective calcium current blocker than previously studied compounds and suggest that it may be useful both as an experimental and a therapeutic tool.