Testosterone and dihydrotestosterone in amniotic fluid and foeto-placental membranes from the guinea pig.

Testosterone (T) and dihydrotestosterone (DHT) in the amniotic fluid (AF) and foeto-placental membranes (FPM) (yolk-sac + amnion) from 180 male and female guinea-pig foetuses were determined by radioimmunoassay on days 28, 32, 36, 40, 44, 48, 52, 56, 60, 64 of gestation. In male foetus the evolution of androgens in the fluid is characterized by two sharp rises, the former at the time of sexual differentiation on day 32 (T = 219.1 +/- 39.1 and DHT = 74.7 +/- 10.0 fmol/ml) the latter, which affects only DHT, on day 52 (DHT = 68.5 +/- 10.3 fmol/ml). In female foetus, AF T concentrations (mean = 36.3 fmol/ml) are comparable to the lowest T concentrations observed in male, while DHT concentrations (less than 2.5 fmol/ml), are significantly lower than those observed in the male (mean = 28.9 fmol/ml) and without any overlap in the values. Thus, in guinea pig, DHT, but not testosterone allows to predict accurately the foetal sex at any stage studied. Testosterone and DHT are also present in FPM and their concentrations were comparable for male and female foetuses in most stages, values varying between 400 and 1600 fmol/g of tissue with a light predominance of DHT compared with T; in both sexes, general evolution of androgens is marked by a rapid drop between days 28 and 44 followed by a significant increase between days 44 and 64. Possible origins of androgens in AF and FMP are discussed.