title: Caffeine-induced inhibition of calcium channel current in cultured smooth cells from pregnant rat myometrium.
abstract: 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 IC50 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 (+)-[3H]-isradipine to myometrial membranes. The IC50 value found in binding experiments was similar to the IC50 value for half-maximal inhibition of calcium channel current. Caffeine decreased the maximal binding capacity of (+)-[3H]-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.
authors.affiliation: INSERM J.F. 88-13, Université de Bordeaux II, France.
authors.forename: C
authors.initials: C
authors.lastname: Martin
authors.forename: C
authors.initials: C
authors.lastname: Dacquet
authors.forename: C
authors.initials: C
authors.lastname: Mironneau
authors.forename: J
authors.initials: J
authors.lastname: Mironneau
mesh_terms: D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D002110:Caffeine / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects*; D004594:Electrophysiology; D005260:Female; D066298:In Vitro Techniques; D017275:Isradipine; D007700:Kinetics; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D009215:Myometrium / Q000187:drug effects / Q000378:metabolism; D011247:Pregnancy; D011725:Pyridines / Q000378:metabolism; D051381:Rats; D012508:Sarcolemma / Q000187:drug effects / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D011725:Pyridines; D002110:Caffeine; D017275:Isradipine