Differential actions of gangliosides on gonadotropin and cholera enterotoxin stimulated adenosine 3':5' cyclic monophosphate dependent protein kinase in isolated rat ovarian cells

Abstract

Rat ovarian cells were exposed to cholera enterotoxin, and the effect on progesterone synthesis as well as on protein kinase stimulation was examined. Cholera enterotoxin stimulated ovarian steroidogenesis in a dose dependent manner similar to that of hCG. The stimulation of protein kinase by cholera toxin was followed by a lag period, whereas hCG effect was immediate. Mixed gangliosides, when added to the incubation medium, blocked the cholera enterotoxin-stimulated protein kinase activity and abolished the decrease in exogenous [3H] cyclic AMP receptor activity brought about by the toxin. In contrast, under similar experimental conditions ganglioside addition elicited no effect on protein kinase activation produced by hCG or LH. The data suggest that gangliosides do not appear to be directly involved in gonadotropin binding to ovarian cell membrane and subsequent mediation of physiological response.