Differential action of sulfated glycosaminoglycans on follicle-stimulating hormone-induced functions of cumuli oophori isolated from mice.

Abstract

It was shown previously that follicle-stimulating hormone (FSH)-induced cumulus expansion was suppressed by sulfated glycosaminoglycans (GAGs), and it was suggested that the action of the GAGs was distal to FSH-stimulated elevation of intracellular cyclic adenosine monophosphate (cAMP). To test this hypothesis for the site of action, the effects of sulfated GAGs on FSHstimulated intracellular cAMP levels were measured by radioimmunoassay. The results showed that the sulfated GAGs, heparmn and chondroitin sulfate B, used at concentrations that completely inhibit cumulus expansion (100 μg/ml and 5 mg/ml, respectively), did not inhibit FSH-stimulated elevation of intracellular cAMP. The effects of sulfated GAGs on FSH-stimulated incorporation of 3H-choline into cumulus cell-oocyte complexes were determined to further assess the actions of these GAGs on cumulus cell functions. Highly purified FSH, but not highly purified luteinizing hormone (LH) or human chorionic gonadotropin (hCG), stimulated the incorporation of 3H-choline into isolated cumulus cell-oocyte complexes. It was shown that the incorporation of 3H-choline into the complexes was almost entirely the result of cumulus cell, rather than oocyte, function. However, about 25–30% of the radiolabel was transferred from the cumulus cells to the oocytes. FSH-stimulated 3H choline incorporation appeared to be mediated by cAMP since incorporation was also stimulated by dibutyrl cAMP (dbcAMP), cholera toxin, and 3-isobutyl-l-methyl-xanthine. However, unlike the inhibitory effect of sulfated GAGs on FSH-stimulated cumulus expansion, neither heparin (100 μg/ml) nor chondroitin sulfate B (5 mg/ml) inhibited 3H-choline incorporation into cumulus cell-oocyte complexes. In addition, heparin did not inhibit FSH-stimulated anabolism of the 3H-choline into phosphatidylcholine. It was concluded that the action of sulfated GAGs on FSHstimulated functions of cumulus cells is differential and that its inhibitory action on cumulus expansion is exerted distally to FSH-stimulated elevation of intracellular cAMP.