Testosterone Secretion by the Early Fetal Pig Testes in Organ Culture

The production and secretion of testosterone by fetal pig testes in vitro was investigated at the stage of sexual differentiation. Single gonads from 76 fetal pigs between 2.0 and 5.2 cm crown-rump (C-R) length were cultivated for 36 h on synthetic TC Medium 199. Steroids were extracted from the media (n = 72) and explants (n = 46) with methylene chloride. Contralateral gonads (n = 58) were extracted without cultivation. Testosterone was isolated by partition chromatography on Celite and measured by a competitive protein-binding radioassay. The earliest stage of fetal development at which testosterone was detected in the gonad (>0.5 ng/gonad, n = 6) was at 2.2–2.3 cm C-R length. Greater quantities of the hormone (P<0.01) were found in the explant (1.6 ± 1.0 ng/gonad, n = 6) and medium (32 ± 21 ng/dish, n = 11) at this stage. High levels were obtained in fetuses between 3.2 and 3.9 cm C-R length; mean values (± S.D.) at the peak for testosterone in the uncultivated testes, the explanted testes and the media were 4.0 ± 1.7 ng (n = 8), 29 ± 3.6 ng (n = 8) and 271 ± 48 ng (n = 4), respectively. In spite of greater testes weight, lesser quantities of testosterone were present in extracts from testes and media for the larger fetuses (>4.0 cm C-R length). It was concluded that the fetal pig testis is capable of secreting testosterone and shows a peak in this activity at the stage of sexual differentiation.