Caffeine‐induced inhibition of calcium channel current in cultured smooth muscle 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 voltagedependent calcium channels in myometrial cells and, in turn, inhibits calcium influx.

Caffeine and Ryanodine May Act on the Plasma Membrane of the Circular Muscle at the Flexure Region in the Guinea-Pig Colon.

“…The similar inhibitory action of caffeine has been reported in rat aortic smooth muscle (Sato et al . , 1988) and in the cultured smooth muscle cells from the pregnant rat myometrium (Martin et al . , 1989 ).…”

Pharmacological Modulation of Sarcoplasmic Reticulum Function in Smooth Muscle

“…Second, caffeine can inhibit plasmalemmal Ca L in cultured myometrial cells from pregnant rats (Martin et al, 1989). In these cells, caffeine inhibits the depolarizationinduced Ca 2ϩ current with an IC 50 value of 35 mM.…”

Different Ion Channel Control pH6‐Induced Bronchoconstriction and Calcitonin Gene‐Related Peptide Release in the Guinea‐Pig Lung

“…Caffeine, at specific concentration used, could induce inhibitory effect on smooth muscle contraction (Missiaen et al 1992). Moreover, Martin et al (1989) demonstrated that caffeine could inhibit voltage-dependent Ca2+ channel in cultured myometrial cells. The caffeine concentration used in our study could have been too low to ensure smooth muscle contraction since caffeine stimulate Ca-induced Ca release mechanism at concentration superior to 1 mM (Iino 1 990 b) .…”