EFFETS DE L'ABLATION DE LA THYROIDE MATERNELLE OU FOETALE SUR LE TAUX DES HORMONES CIRCULANTES CHEZ LE FOETUS DE RAT

Abstract

ABSTRACT The BEI was determined in maternal and foetal rat plasma on day 21 of gestation by an isotope equilibrium method. The foetuses were either left intact or deprived of their thyroid gland by decapitation ; the mothers were either normal or thyroidectomized. The thyroid gland of the foetal rat appears to be the main source of thyroid hormone present in the foetal blood: thyroidectomy of the mother does not alter the BEI level of normal foetuses. The ablation of the foetal thyroid gland markedly decreases the foetal BEI both in intact and thyroidectomized mothers. The BEI level in plasma of decapitated foetuses is lower in thyroidectomized mothers than in intact mothers. Hence, some maternal hormone passes through the placenta into the foetus, but this transfer is too limited to compensate for the absence of the foetal thyroid gland.