Effect of cocaine on intracellular calcium regulation in myometrium from pregnant women

OBJECTIVE: To evaluate the effect of cocaine on intracellular free calcium ([Ca2+](i)) regulation in human myometrial cells by determining the sources of Ca2+ it might mobilize, as well as assess the role cocaine might play i n the catecholamine's effect on the cell's [Ca2+](i). METHODS: Primary culture of myometrial cells from pregnant women was used a s an experimental model. [Ca2+](i) relative changes in response to cocaine and norepinephrine were measured with fura-2 fluorometry and analyzed by me ans of one-way analysis of variance. RESULTS: Cocaine alone (10(-8) to 10(-3) mol/L) increased [Ca2+](i) by up t o 43 +/- 18% over basal level in a dose-dependent manner. Norepinephrine al so elevated [Ca2+](i) in a concentration-dependent manner (202 +/- 24% over vasal level at 10(-4) mol/L). the norepinephrine-evoked increase was inhib ited in Ca2+-free media by 48%, whereas the cocaine response was not affect ed. The Ca(2+-)channel antagonist nifedipine caused decrease in the [Ca2+]( i) response to 10-(5) mol/L of norepinephrine by 84%, whereas the [Ca2+](i) rise to 10(-5) mol/L cocaine was not significantly changed. Inhibitor of t he sarcoplasmic reticulum Ca2+ pump, thapsigargin, completely blocked cocai ne-evoked increases in [Ca2+](i), whereas norepinephrine responses were gre atly reduced. At the same time, cocaine (10(-8) to 10(-3) mol/L) did not po tentiate norepinephrine-evoked Ca2+](i) increases in the cells. CONCLUSION: These results indicate that cocaine increases [Ca2+](i) in preg nant human myometrial cells, primarily by stimulating release of Ca2+ from intracellular stores rather than by direct stimulation of Ca2+ influx. Copy right (C) 1999 by the Society for Gynecologic Investigation.