Expression and regulation of transforming growth factor beta1 mRNA and protein in rat fetal testis in vitro

The expression and secretion of Transforming Growth Factor beta1 (TGFbeta1) by cultured testes of day 20.5 rat fetuses were investigated. The testes were found to express two TGFbeta1 mRNA transcripts of 2.5 and 1.8 kb. By using mink lung epithelial cell bioassay based on the measurement of the inhibition of tritiated thymidine incorporation in response to TGFbeta1 immunoreactive material, the fetal testes were shown to secrete TGFbeta1 protein in organ culture. This secretion was positively regulated by dibutyryl cyclic AMP or by LH and FSH together, but not by LH alone and very slightly by FSH alone, which suggests interactions between Leydig and Sertoli cells for the control of TGFbeta1 production. These regulations probably take place at a posttranscriptional step since no concomitant increase of TGFbeta1 mRNA levels was observed. Such a positive regulation of TGFbeta1 secretion by gonadotropins could be a characteristic of the rat fetal testis.