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Caffeine‐induced inhibition of calcium channel current in cultured smooth muscle cells from pregnant rat myometrium
Author(s) -
Martin C.,
Dacquet C.,
Mironneau C.,
Mironneau J.
Publication year - 1989
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1989.tb12622.x
Subject(s) - isradipine , caffeine , chemistry , calcium , myometrium , calcium channel , depolarization , biophysics , voltage dependent calcium channel , ic50 , endocrinology , medicine , t type calcium channel , membrane potential , pharmacology , biochemistry , dihydropyridine , in vitro , biology , uterus , organic chemistry
1 The inhibitory effect of caffeine on the calcium channel current was investigated in cultured myometrial cells isolated from pregnant rats. 2 Caffeine inhibited the calcium channel current elicited from a holding potential of — 70 mV in a concentration‐dependent manner. The IC 50 was estimated to be 35 mM. 3 The caffeine inhibition was not enhanced when calcium channels were opened by a conditioning depolarizing pulse sequence or when the number of inactivated calcium channels was increased at depolarized holding potentials. 4 Caffeine antagonized the specific binding of (+)‐[ 3 H]‐isradipine to myometrial membranes. The IC 50 value found in binding experiments was similar to the IC 50 value for half‐maximal inhibition of calcium channel current. Caffeine decreased the maximal binding capacity of (+)‐[ 3 H]‐isradipine to myometrial membranes without any significant change in the dissociation constant. 5 The results indicate that caffeine interacts with a site closely associated with the voltage‐dependent calcium channels in myometrial cells and, in turn, inhibits calcium influx.