Hyperpolarization and slowing of the rate of contraction in human uterus in pregnancy by prostaglandins E2 and F(2α): Involvement of the Na pump

Abstract

1. The effects of prostaglandins E2 (PGE) and F(2α) (PGF) on membrane potential and isometric tension and cytoplasmic free calcium concentration ([Ca2+](i)) and tension were studied in strips of uterine smooth muscle obtained from women undergoing Caesarean delivery at term and during established labour. 2. Prostaglandins (PGs) evoked a biphasic response. The excitatory component consisted of depolarization of the membrane, which initiated spike action potentials, an increase in [Ca2+](i) and tension development. The membrane remained depolarized at -19 ± 1 mV for about 2 min, then repolarised abruptly, [Ca2+](i) promptly returned to basal levels, and tension development ceased. 3. This comp..