Testosterone, dihydrotestosterone, androstenedione and dehydroepiandrosterone concentrations in placentae, ovaries and plasma of the rat in late pregnancy

Abstract

Testosterone (T), dihydrotestosterone (DHT), androstenedione (.DELTA.4) and dehydroepiandrosterone (DHA) were measured by radioimmunoassay in peripheral plasma, uterine vein plasma, ovary and placentae within the last 3-4 days of pregnancy in Spragus-Dawley rats. In the uterine vein, T and .DELTA.4 levels were significantly higher than those reported in the peripheral plasma at any particular day of late pregnancy. In peripheral plasma as in uterine vein plasma .DELTA.4 and T gradually decreased from day 20 to term (-63% for .DELTA.4 and approximately -45% for T) while DHT concentrations were unchanged. This decline is concomitant with a similar pattern of change in the placentae; indeed placental concentrations of .DELTA.4 and T decreased significantly from day 19 to 22 (-63 and -79%, respectively) and were positively correlated with the levels of both androgens in uterine venous and peripheral plasma. In the late phase of pregnancy in the rat circulating .DELTA.4 and T originate from placentae. In contrast, ovarian androgen concentrations showed a sharp increase from day 21 to term: 58% for DHA, 49% for .DELTA.4, 87% for T and 24% for DHT. Apparently these increasing concentrations of ovarian androgens could be related to the next ovulatory cycle.