Effect of Foetal Hypophysectomy on Catecholamine Levels in the Lamb Adrenal during Prolonged Gestation

Abstract

DESTRUCTION of the pituitary gland of the foetal lamb in utero results in an indefinite prolongation of pregnancy¹. This seems to be caused by a reduction in the secretion from the foetal adrenal cortex, for parturition can be induced in either post-mature hypophysectomized lambs or premature normal foetuses by infusions of ACTH or of large doses of cortisol into the foetus². There is, however, a close association between the adrenal cortex and the concentration of adrenaline in the adrenal medulla^3–6. In the lamb the rapid growth of the adrenal cortex immediately before birth is accompanied by a slight rise in the proportion of adrenaline in the gland⁷; absence of growth of the adrenal cortex after hypophy-sectomy might therefore affect catecholamine content, or more specifically the ratio of adrenaline to noradrenaline in the medulla, particularly during the period of prolonged gestation. This possibility has been investigated in the present experiments in which foetal hypophysectomy in utero was carried out at 93–105 days gestation in sixteen Welsh ewes.