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

Abstract The effects of pincainide, a new β-amino anilide, on contractile responses and 45 Ca 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 Ca 2+ -induced contractions of K + -depolarized aorta as well as the spontaneous mechanical activity of portal veins were also inhibited by pincainide. Pincainide (5 × 10 −3 M) inhibited the 45 Ca influx stimulated by 10 −6 M NA and increased 45 Ca efflux. It was concluded that in isolated rat aorta, pincainide not only inhibited the influx of Ca 2+ reducing the contractile responses to NA and high K + but it also inhibited other effects related to NA-induced release of intracellular Ca 2+ stores.