Testosterone levels in umbilical cord blood, maternal peripheral plasma and amniotic fluid of the crab-eating monkey (Macaca fascicularis)

rone (AFT) and maternal peripheral plasma testosterone were radioimmunologically assayed. (1) In 57-day male fetuses, UAPT level was 3 to 4 ng/mi ; it dropped to 0.5 to 1 ng/ml near 75 days and stayed at that level until term. This content in female fetuses remained at about 1 ng/mi throughout gestation (fig. 1). (2) During the second-half of gestation, UVPT content was generally lower than UAPT content, whatever the fetal sex (table 1). (3) AFT level was clearly lower than UAPT or UVPT level ; it stayed under the sensitivity limit of the assay method in most of the female fetuses. The AFT concentration curve in male fetuses was parallel to that of UAPT (fig. 2). The correlation coefficient (r = 0.71) (fig. 3), together with the relatively large quantities of AFT in 37 to 50-day male fetuses, suggested that the fetal testis could secrete testosterone at a very early stage when the Leydig cells were not yet recognizable. (4) There was no relation between maternal testosteronemia and the sex of the conceptus at any time during gestation (fig. 4).