Effects of progesterone, estrone, estradiol, estriol and dehydroepiandrosterone sulphate on phosphoinositide-specific phospholipase C activity from human myometrium

Abstract

Phosphoinositide-specific phospholipase C (PLC) was partially purified as three fractions (PLC 1, 2 and 3) from gestational human myometrium homogenate by a series of centrifugation, dialysis and high performance liquid chromatography. These fractions varied in their apparent molecular weigh, affinity to anion exchanger but showed similar Ca²⁺ dependence and pH profile. At a concetration of 10^-6M progesterone, estrone or estriol suppressed phosphatidyl inositol 4, 5-bisphosphate (PIP₂) hydrolyzing activity of PLC1 and PLC3 to 52-92% of control. The same concentration of dehydroepiandrosterone sulphate stimulated the activity of PLC3 slightly. These findings indicate the presence of direct effects of these gestation related steroids on excitation-contraction (E-C) coupling in myometrium through the inhibition of PLC _s in PI response pathway, suggesting dissociation of the E-C coupling by this inhibition as a possible mechanism for hormone-suppressed myometrial contraction during pregnancy.