Secretion of activin by interstitial cells in the testis

Abstract

Activin, a dimer formed by the β subunits of inhibin, has an effect that is opposite to that of inhibin in a number of biological systems. Which cell types secrete activin in vivo is not known. TM3 cells, a Leydig-derived cell line, contained messenger RNAs that hybridized with human β(A) and β(B) complementary DNA probes and were similar in size to the porcine messenger RNA for the β subunits of inhibin. No hybridization to the inhibin α subunit was detectable in the TM3 cells. Conditioned medium from TM3 cells and from primary cultures of rat and porcine interstitial cells stimulated the release of follicle-stimulating hormone in a pituitary cell culture assay. It is likely that, in the testis, the Leydig cells secrete activin and the Sertoli cells produce inhibin, or a combination of both.