Calcium antagonistic action involved in vasodilation by brovincamine

Abstract

o 1. 1. Possible mode of vasodilative action of brovincamine was assessed in isolated cardiovascular preparations in comparison with verapamil and papaverine. 2. 2. Brovincamine (IC 50: 1.2 × 10 −5 M), verapamil (IC 50: 3.5 × 10 −7 M) or papaverine (IC 50: 2.5 × 10 −5 M) caused a dose-dependent relaxation of potassium (30 mM)-contracture in the rabbit pulmonary arterial segment. This relaxation by verapamil or brovincamine, but not by papaverine, was antagonized by increasing external Ca 2+ concentration to 12.4 mM. 3. 3. Duration of slow action potentials of partially depolarized guinea-pig papillary muscle was reduced by 15 min exposure to brovincamine (5 × 10 −5 M) or verapamil (10 −5 M). 4. 4. These results suggest that brovincamine produces a vasodilation via a slow Ca 2+-channel blockade.