Altered bioelectrical and mechanical activities of rat gastric smooth muscle preparations by inhibiting enterocytogenin.
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.
Trifonov
B B
BB
Department of Physiology, Medical University of Plovdiv, Bulgaria.
Kristev
A
A
Roussev
G K
GK
Kamberov
E S
ES
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001030:Apamin / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004232:Diuretics / Q000494:pharmacology; D004594:Electrophysiology; D005753:Gastric Mucosa / Q000378:metabolism; D007422:Intestines / Q000737:chemistry; D008566:Membranes / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology*; D051381:Rats; D013270:Stomach / Q000187:drug effects
D002121:Calcium Channel Blockers; D004232:Diuretics; D010455:Peptides; D001030:Apamin; D002110:Caffeine; D000584:Amiloride; D009543:Nifedipine; D002118:Calcium; D009638:Norepinephrine