SOMATOMEDIN-C (Sm-C) RECEPTORS IN CULTURED PIG LEYDIG CELLS (LC)|[colon]| CHARACTERIZATION AND REGULATION. ROLE OF Sm-C ON LC FUNCTIONS

摘要

Using affinity cross-linking we have shown the presence of Sm-C receptors (Cm-C-R) in cultured pig LC. The Sm-C-R were further characterized by competition binding (KD 1.10?9 M). When LC were cultured in a chemically defined medium without hormones, the number of Sm-C-R varied from 10000 to 15000 sites/cell. Treatment of LC with hCG induced a 2 to 3 fold increase in Sm-C-R. This effect was time-(maximum effect after 48 h) and dose-dependent (ED50 = 10?10 M). Moreover LC treatment with Sm-C for 3 days induced an increase of hCG receptors (4-6 fold) and of hCG responsiveness (cAMP and testosterone production) (8-10 fold) with ED50 of about 2 ng/dl. In addition, Sm-C stimulated LC DNA synthesis (ED50 ? 10 ng/ml). These results show : 1) LC contain specific Sm-C-R which are positively regulated by hCG; 2) Sm-C increased both hCG receptors number and hCG steroidogenic responsiveness of LC. Since Sertoli cells secrete Sm-C (see Chatelain et al) our data strongly suggest that Sm-C might play a role in the paracrine regulation of LC. Therefore Sm-C could play a key role on the delayed puberty observed in children with isolated growth hormone deficiency.