Transfer of maternal testosterone to the guinea pig fetus during the last third of pregnancy.

Testosterone (T) transfer from mother to fetuses was explored in anesthetized guinea pigs on Days 48 and 67 of pregnancy using a constant intravenous infusion of tritium-labeled T ([3H]T). Labeled dihydrotestosterone ([3H] DHT), androstenedione ([3H] delta 4) and [3H] T were estimated after celite chromatography in maternal plasma, umbilical venous plasma, fetal arteriovenous plasma and fetal tissue homogenates including liver, genital tract with gonads, hypothalamic area, hypophysis and remaining brain. Total radioactivity was measured by counting a part of the homogenates. Results indicate that very low concentrations of [3H] T and [3H] delta 4 were found in umbilical and fetal plasma, whereas [3H] DHT levels were relatively high. A minute part of maternal T was transferred to male and female fetuses: 0.7 to 1.9 pg/ml, and that represented 0.4 to 5.6% of fetal T. The difference observed between umbilical and fetal [3H] T showed that 80% of the fetal T coming from the mother was metabolized by the fetuses. This result is discussed in relationship to the high radioactive concentrations present in fetal liver. Concentrations of total radioactivity were high in fetal tissues, and the three nervous tissues exhibited a significant difference in their capacity to fix radioactivity. There was a complete absence of the three labeled androgens in the hypophysis. However, [3H] DHT was present in all other tissues, and gonads + genital tract in the male fetus exhibited [3H] DHT concentrations significantly higher than those detected in the female fetus.(ABSTRACT TRUNCATED AT 250 WORDS)