The effects of La2+ on spontaneous contraction, and the contraures induced by 0mM Na, 60mM K, Ca(1, 2, 4mM) and 10E-6M acetylcholine, 1mM caffeine were studied in order to elucidate diverse actions of La2+ on the Ca ion mobilization related
with
contraction in a dose-dependent manner(3?10E-5 M-3x?10E-3 M). Ca-induced contracture tension increased according to the increment of extrcellular Ca ion concenrtration(1, 2, 4mM) but was suppressed proportional to the
concentrations of La3+(10E-M, 10E-3M). The contracture induced by 60mM K-Y yrode solution was composed of a phasic and a tonic response, the response was suppressed by 10E-4M La3+ La3+ also supressed 10E-6 acetylcholine-induced
conracture composed of repectitive phasic and a tonic component and 1mM caffeine-induced contracture.
Na-free contracture but from 10E-3 M suppressed the amplitude in the concentration of 3?10E-3 From the above results, it is suggested that La3+ may inhibit not only Ca2+ influx via leak Ca2+-channel, voltage sensitive Ca2+-channel and
receptor=operated Ca2+, against Ca2+ but also intracellular Ca2+ release from the sarcoplasmic reticulum in the antral circular muscle of guinea-pig stomach.
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