RESUMO
Inhibiting enterocytogenin (IEG), a 4.5 kDa nucleopeptide isolated from pig intestinal mucosa induced dose-dependent alterations in the spontaneous contractile and bioelectric activities of rat gastric smooth muscle when applied at 10(-8) to 10(-4) M. Two separate phases were apparent in the effects observed, an initial contractile phase followed by a relaxation phase. The depolarization and the related contraction were reduced by amiloride and to a lesser extent by nifedipine. This reduction resulted in a corresponding decrease in the magnitude of the subsequent relaxation phase. Charybdotoxin and apamin caused a statistically significant decrease in the hyperpolarization and the magnitude of the relaxation phase and increased the duration of the contractile phase. On a caffeine or noradrenaline background the effects induced by IEG were diminished, suggesting that they are mediated through Ca2+ release from the intracellular Ca2+ stores. We hypothesize that the depolarization induced by IEG involves activation of the voltage-dependent Ca2+ channels with subsequent stimulation of the Ca(2+)-dependent K+ channels and late development of hyperpolarization.