Electron microscopic study of the overlapping effect of thyrotropin and gonadotropins on the Sertoli cells of chick embryo.

The ultrastructural features of the Sertoli cells of the embryonic chick testis have been studied following the administration of thyrotropin (TSH) and gonadotropins (FSH + LH), on the 8th or 15th day of embryonic life. The principal changes observed in the 15-day TSH-treated embryos were the increased quantities of Sertoli cell organelles, particularly the agranular endoplasmic reticulum, mitochondria and Golgi complex. Although the same changes were observed in the gonadotropins-treated embryos, it is worthwhile to mention that the Sertoli cells of 15-day TSH-treated embryos contain abundant granular endoplasmic reticulum more than that in the gonadotropin treated ones. The most striking ultrastructure feature, the occurrence of coated vesicles in Sertoli cells in all groups including control, however they appear much numerous in 15-day treated embryos. The findings of the present investigation support the hypothesis that TSH has an extrathyroidal role and demonstrate the functional responsiveness of 15-day chick embryo Sertoli cells to this hormone. The FSH-like activity of TSH agrees with our earlier hypothesis: namely that hormones of similar molecular structure may bind to the same binding sites as a consequence of receptor immaturity.