REGULATION OF 5-ALPHA-REDUCTASE ACTIVITY IN CULTURED IMMATURE LEYDIG-CELLS BY HUMAN CHORIONIC-GONADOTROPIN

The present studies examined the hormonal regulation of 5α-reductase activity in cultured immature rat Leydig cells. Within the testis 5α-reductase was concentrated in the interstitial cell compartment, and among interstitial cells, the enzyme was localized primarily in Band 3 of Percoll density gradients, which contains the majority of Leydig cells. Among various factors reported previously to stimulate testicular 5α-reductase activity when administered in vivo to immature rats (LH/hCG, FSH, luteinizing hormone releasing hormone or prolactin), only LH/hCG directly stimulated 5α-reductase activity of cultured immature Band 3 cells. Neither growth hormone which was reported previously to stimulate hepatic 5α-reductase activity, nor insulin, insulin-like growth factor-I, or epidermal growth factor, which have been reported to modulate Leydig cell function, had any effect on 5α-reductase activity of Band 3 cells. These studies suggest that the major factor directly stimulating 5α-reductase activity in Leydig cells during early maturation is LH. However, it is possible that other factors acting indirectly may modulate the maturational rise in 5α-reductase activity. © 1990.