Biomedical subjects
Publications and source records attributed to P Corbier.
The changes in serum testosterone and dihydrotestosterone concentrations have been measured in the newborn Rat, before, during and up to 6 hrs after birth. A sudden and transient increase of serum testosterone has been found between 0 and 2 hrs. At 4 hrs, the value returns to that found in the foetus at the end of gestation.
The evolutions of serum LH and FSH concentrations and of testicular weight have been measured in the newborn Rat before, during and up to 24 hrs. after birth. A sudden and transient increase of LH and FSH is observed at birth. The testicular weight rises rapidly between 2 and 4 hrs.
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The variations of the testicular responsiveness to hCG and the implication of the maternal estrogens in the functioning of the testes were studied in the perinatal male rat. Male rat fetuses treated with hCG at the end of gestation failed to show an increase in serum testosterone (T). The lack of testicular responsiveness to hCG in the fetus is neither due to anesthesia nor to a blocking effect of estrogens directly on the testes. On the other hand, hCG injected either at 4 h or at 48 h after birth increases serum T. The administration of 5 micrograms of estradiol 17 beta (E2) to the newborn male rat at the time of birth blocks the expression of the postpartum testosterone surge. The fall in the plasma estrogens and the increase of the testicular sensitivity to gonadotropic stimulation at the time of birth are factors which are very likely implicated in the determinism of the neonatal testicular hyperactivity.
In the rat an abrupt discharge of testicular testosterone in the newborn male figures prominently in the development of mechanisms controlling gonadotropin secretion, sexual behavior, and also promotes the functional differentiation of the accessory sex glands. In this study we detail the temporal characteristics of this surge in the rat, and we provide comparative data documenting a similar surge-like appearance of testosterone in neonatal male mice, recently foaled male horses, and newborn human infants. Although the physiological and behavioral significance of this phenomenon for species other than the rat remains to be determined, the apparently ubiquitous appearance of the neonatal testosterone surge suggests that it may be of special significance in the sexual differentiation of many mammalian species.