Testosterone secretion by foetal rat testes in vitro.

Testosterone secretion by foetal rat testes (13 1/2-21 1/2 days of gestation) explanted for 3 days in a synthetic medium was measured every 24 h by radioimmunoassay. During the first day of explantation, the foetal testis produced, respectively, 1013 +/- 132, 8734 +/- 1118, 9179 +/- 2185 and 3886 +/- 309 (S.E.M.) pg/testis when explanted at 14 1/2, 16 1/2, 18 1/2 and 21 1/2 days respectively. Testosterone production by 13 1/2-day-old testes was not detectable on the first day of culture, but appeared on subsequent days. Daily testosterone secretion increased on the 2nd and 3rd days of culture in 14 1/2-day-old testes and decreased in older stages. These results suggest that the functional differentiation of the testis is independent of stimulatory factors like gonadotrophins. Dibutyryl cyclic AMP was found to stimulate testosterone production significantly from 14 1/2 days of gestation onwards.