Effect of isoproterenol on uptake of calcium-45 by pregnant human and rat myometrium

Abstract

Rat and human myometria contract is response to substitution of external Na+ with Li+. This contraction was accompanied by elevation of 45Ca uptake in rat but not human uterus. The lanthanum technique failed to demonstrate elevation of cellular 45Ca in human myometrium by Li+ substitution. It also failed to demonstrate reduction of Li-elevated 45Ca uptake by isoproterenol or drugs considered to inhibit calcium influx, in rat myometrium although these drugs prevented Li-induced contraction. In human myometrium, isoproterenol increased 45Ca uptake. This probably represents increased extracellular calcium binding. Isoproterenol relaxed depolarized human myometrium provided that the external calcium had been removed for 15 minutes.