Influence of Cortisol on Trophic and Corticosteroidogenic Actions of Adrenocorticotrophin on Foetal Adrenals

Abstract

The treatment of female rats with corticosteroids during pregnancy, causes atrophy of the foetal adrenals (see Jost, 1966;Skebelskaya, 1968) and decreases the corticosterone content of the adrenals (D'Angelo, Paul & Wall, 1973). Corticosteroids are able to cross the placenta from the mother to the foetus. Adrenal atrophy also occurs when rat foetuses are injected with corticosteroids (see Jost, 1966). This effect is attributed to the blocking action of corticosteroids on the corticostimulating activity of the foetal hypophysis and not to the direct action of corticosteroids on the foetal adrenals. This hypothesis is supported by the atrophy of the foetal pituitary gland (see Jost, 1966) and by the decrease of its adrenocorticotrophin (ACTH) content (Skebelskaya, 1968) when mothers or foetuses are treated with corticosteroids. Moreover, foetal adrenal weight increases when foetuses are injected with cortisol and ACTH (Jost, 1957). Corticosteroids also prevent the adrenal hypertrophy observed after the treatment of the mother with inhibitors of steroidogenesis (Dupouy, 1971).The aim of this work was to verify whether corticosteroids could interfere directly with the trophic and corticosteroidogenic actions of ACTH at the level of the foetal adrenals. Both effects of ACTH were compared in decapitated rat foetuses, with and without cortisol administration.Twenty-one-day-old rat foetuses of the Wistar strain, were decapitated in utero, under pentobarbitone anaesthesia, and injected s.c. 30 min later with either l-6mu. porcine ACTH in 0-9% saline or with the same volume of saline only. Some foetuses were previously injected with cortisol acetate (600 µg) either just at the moment of decapitation or 30 min after this operation just at the time of the ACTH injection. Corticosterone determinations in the adrenals were made by the fluorometric method of Guillemin, Clayton, Lipscomb & Smith (1959).The corticosterone contents of the adrenals of the decapitated and non-cortisol-treated foetuses, increased lOmin after ACTH injection (Fig. 1). This response to ACTH was not impaired by cortisol treatment for 10 or 40 min (Fig. 1). The body and adrenal weights of the foetuses were not altered by the operation.Other foetuses were decapitated on day 20 of pregnancy and injected with 0-9% NaCl solution or with cortisol (600Mg). On day 21, the adrenals of the saline-treated foetuses were as atrophied (l-96±0-09 (s.EM.)mg, 8 cases) as those of the cortisol-treated foetuses (1-80 ±0-08 mg, 14 cases) when compared with the adrenals of the foetuses of the same age, decapitated on day 21 and injected with saline (2-44±0-10mg, 12 cases) or cortisol (2-51 ±0-11 mg,7 cases). Moreover, their adrenals contained little corticosterone (Fig. 1). The response of the decapitated foetuses to ACTH treatment was not affected by previous