DEVELOPMENT OF TESTOSTERONE SECRETION IN THE FETAL PIG TESTIS

Secretion of testosterone by fetal testes of domestic pigs was studied by organ culture and radioimmunoassay of steroids extracted from the culture medium. Gonads were taken from pig embryos ranging in size from 1.8-2.7 cm crown-rump (C-R) length, to span the period of gonadal sex differentiation. Explants were cultivated in biologically supplemented medium for 12 days, with 4-5 changes of medium; one member of each pair of gonads was grown in medium containing 10 IU human chorionic gonadotropin (hCG). No testosterone was found for the first several days with control gonads from the earlier stages of development. An onset and increase in testosterone secretion was noted in the second half of the cultivation (>6 days) for gonads from embryos of 1.8 and 1.9 cm mean C-R length. Production of testosterone by explants from fetuses of 2.0 cm C-R length rose from 0.3 ± 0.03 to 12.7 ± 5.1 ng/24 h/gonad during 12 days (mean ±SD, n=5). Secretion by control testes of larger fetuses (2.7 cm C-R) was >175 ng/24 h for the initial period (1.5 days), but decreased subsequently. In all instances, hCG in the medium resulted in an immediate onset or increase in testosterone secretion depending on the fetal size at explantation of the gonads. These findings suggest that testosterone synthesis in the differentiating male gonad may be initiated independently of gonadotropin control. The onset of testosterone secretion, moreover, seems to occur at a later stage of development than that at which androgen production can be stimulated by gonadotropins in vitro.