A novel role for somatomedin-C in the cytodifferentiation of the ovarian granulosa cell.
The role of somatomedin-C (Sm-C) in the acquisition of granulosa cell progesterone biosynthesis was investigated in vitro in a primary culture of rat granulosa cells cultured for 72 h under serum-free conditions. Basal progesterone accumulation was negligible and remained unaffected by treatment with highly purified Sm-C (50 ng/ml). Whereas treatment with FSH (20 ng/ml) produced a 9-fold increase in progesterone accumulation, the concurrent application of increasing concentrations (0.3-50 ng/ml) of Sm-C brought about dose-dependent increments in the FSH-stimulated accumulation of progesterone with a median effective dose of 4.0 +/- (SE) 0.3 ng/ml and a maximal response 9.6-fold greater than that induced by FSH alone. A monoclonal antibody raised against Sm-C (sm 1.2) produced complete immunoneutralization of the synergistic interaction between FSH and Sm-C, supporting the specificity of the Sm-C effect and arguing against the possible involvement of copurified contaminant(s) in the preparation used. Treatment of granulosa cells with the highest dose of Sm-C tested (50 ng/ml), in the absence or presence of FSH, did not result in significant alterations in cell number, DNA content, plating efficiency or viability. Taken together, our findings indicate that Sm-C is capable of synergizing with FSH in the induction of granulosa cell progesterone biosynthesis. Significantly, this ability of Sm-C to augment differentiated phenotypic expression of the developing granulosa cell is distinct from its well established growth-promoting property and may thus represent a novel biologic effect of this polypeptide.
D000818:Animals; D000911:Antibodies, Monoclonal; D002452:Cell Count; D002454:Cell Differentiation; D004305:Dose-Response Relationship, Drug; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D006107:Granulosa Cells / Q000166:cytology* / Q000187:drug effects; D007334:Insulin-Like Growth Factor I; D011374:Progesterone / Q000096:biosynthesis; D051381:Rats; D013002:Somatomedins / Q000276:immunology / Q000502:physiology*
D000911:Antibodies, Monoclonal; D013002:Somatomedins; D011374:Progesterone; D007334:Insulin-Like Growth Factor I; D005640:Follicle Stimulating Hormone