Enhanced stimulation of 5 alpha-reductase activity in cultured Leydig cell precursors by human chorionic gonadotropin.

Previous studies have demonstrated that the increase in number of Leydig cells during prepubertal maturation results, in part, from the differentiation of mesenchymal precursors between the second and fourth week of postnatal life. After conversion to immature Leydig cells, they actively synthesize testosterone, but this androgen does not accumulate because high 5 alpha-reductase activity rapidly converts testosterone to 5 alpha-reduced metabolites. The present studies examined whether the conversion of precursor cells to immature Leydig cells in vitro by human chorionic gonadotropin (hCG), as characterized by progressive increases in testosterone formation and 5-ene-3 beta-hydroxysteroid dehydrogenase-isomerase (3 beta-HSD) activity, is associated similarly with an enhanced stimulation of 5 alpha-reductase activity.

Evidence that both receptor- and heparan sulfate proteoglycan-bound basic fibroblast growth factor are internalized by cultured immature Leydig cells.

The present studies examined how 125I-labeled basic fibroblast growth factor (bFGF) bound to high affinity receptors and with lower affinity to heparan sulfate proteoglycans (HSPG) of cultured immature rat Leydig cells was processed. Following incubation for 2 h at 4 degrees C with 125I-bFGF, cells were washed to remove unbound radioactivity. Fresh medium was added, and cells were incubated at 4 degrees and/or 37 degrees C.

Evidence that biphasic effects of basic fibroblast growth factor on 5-ene-3 beta-hydroxysteroid dehydrogenase-isomerase activity in cultured immature Leydig cells are mediated by binding to heparan sulfate proteoglycans.

The present studies examined the effects of heparin, heparinase, insulin or insulin-like growth factor-I on basic fibroblast growth factor actions on 5-ene-3 beta-hydroxysteroid dehydrogenase-isomerase activity of cultured immature rat Leydig cells. Treatment with basic fibroblast growth factor alone (0.025-20 ng/ml) for 2 days had a biphasic effect on enzyme activity, with lower concentrations (0.

Basic fibroblast growth factor-induced increase in 125I-human chorionic gonadotropin binding to luteinizing hormone receptors in cultured immature Leydig cells is mediated by binding to heparan sulfate proteoglycans.

Previous studies have shown that basic fibroblast growth (bFGF) has a biphasic effect on 125I-hCG binding to LH receptors in cultured Leydig cells from immature rats. Low concentrations of bFGF (0.1-1.

Effects of acidic fibroblast growth factor on 5-ene-3 beta-hydroxysteroid dehydrogenase-isomerase and 5 alpha-reductase activities and [125I]human chorionic gonadotrophin binding in cultured immature Leydig cells.

The present studies examined the effects of acidic fibroblast growth factor (aFGF) on 5-ene-3 beta-hydroxysteroid dehydrogenase-isomerase (3 beta-HSD) and 5 alpha-reductase activities and [125I]human chorionic gonadotrophin ([125I]hCG) binding in cultured immature rat Leydig cells. Increasing concentrations of aFGF (0.1-20 ng/ml) progressively decreased basal 3 beta-HSD activity from 0.