Effects of pincainide on contractile responses and 45Ca movements in rat isolated vascular smooth muscle.

The effects of pincainide, a new beta-amino anilide, on contractile responses and 45Ca fluxes were studied in rat aorta and on spontaneous mechanical activity in rat portal veins. Pincainide (10(-5) to 10(-2) M) produced a dose-dependent inhibition of noradrenaline (NA) and high K+ -induced contractions. These inhibitory effects were observed with pincainide added either before or after the induced contractions. The Ca2+ -induced contractions of K+ -depolarized aorta as well as the spontaneous mechanical activity of portal veins were also inhibited by pincainide. Pincainide (5 X 10(-3) M) inhibited the 45Ca influx stimulated by 10(-6) M NA and increased 45Ca efflux. It was concluded that in isolated rat aorta, pincainide not only inhibited the influx of Ca2+ reducing the contractile responses to NA and high K+ but it also inhibited other effects related to NA-induced release of intracellular Ca2+ stores.