Dosage Radioimmunologique De La Testostérone Dans Le Plasma, Les Gonades Et Les Surrénales De Foetus En Fin De Gestation Et De Nolveau-Nés, Chez Le Lapin

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Abstract
A radioimmunoassay was used for measuring testosterone in the plasma, gonads and adrenals of 28, 29, 30 and 31-day-old rabbit fetuses of both sexes and newborns. A marked sex difference was shown in the testosterone concentrations in plasma and gonads while in adrenals the levels of testosterone were low in both sexes (34-147 pg/10 mg). In male fetuses, plasma testosterone levels increased from the 28th (133 .+-. 20 pg/ml) to the 31st day (361 .+-. 119 pg/ml) of intrauterine life, reaching the values observed in the newborns (387 .+-. 73 pg/ml). Plasma from males at all stages contained significantly more testosterone than plasma from female fetuses (21 .+-. 6 to 41 .+-. 11 pg/ml) and female newborns (42 .+-. 6 pg/ml). Fetal testicular testosterone concentrations varying from 1382 .+-. 218 to 2317 .+-. 333 pg/10 mg were similar to those measured in the newborns (1940 .+-. 304 pg/10 mg) and significantly higher than fetal (13-34 pg/10 mg) or neonatal (44 pg/10 mg) ovarian concentrations. The endocrine activity of the fetal testis during this development is discussed.