Endocrine and paracrine control of Leydig cell steroidogenesis and proliferation in the wall lizard: an in vitro study

The present in vitro study, for the first time, demonstrates the endocrine as well as paracrine control of Leydig cell steroidogenesis and proliferation in the wall lizard Hemidactylus flaviviridis. Unlike mammals, Leydig cell activity in the wall lizard seems to be directly controlled by ovine follicle-stimulating hormone (FSH)-like molecule, since FSH increased the testosterone production and tritiated thymidine ([ 3H]TdR) incorporation by Leydig cells. In addition, Sertoli cell paracrine factor or factors play important roles in controlling Leydig cell activities as non-activated Sertoli cell-conditioned medium (SCCM) alone stimulated testosterone production by both non-activated and FSH-preactivated Leydig cells. As far as the proliferation was concerned, non-activated SCCM did not influence [ 3H]TdR uptake by non-activated or FSH-preactivated Leydig cells, while FSH-preactivated SCCM was able to stimulate proliferation of activated Leydig cells. It may be concluded that FSH, besides directly controlling, also regulates Leydig cell activities indirectly through stimulating the secretion of Sertoli cell paracrine factors. Moreover, steroidogenic factor is different from mitogenic factor because non-activated Leydig cells were responsive to steroidogenic factor but nonresponsive to mitogenic factor.