PITUITARY AND BLOOD CORTICOTROPHIN CHANGES IN ADRENALECTOMIZED RATS MAINTAINED ON PHYSIOLOGICAL DOSES OF CORTICOSTEROIDS

Abstract

ABSTRACT Pituitary and blood corticotrophin (ACTH) concentrations were estimated in adrenalectomized rats maintained on cortisol or crude adrenocortical extract (ACE) with and without ascorbic acid. Blood ACTH levels were also determined in similarly treated animals after subjection to mild stress. Thirty days after adrenalectomy there were marked rises in pituitary and blood corticotrophin concentration which were prevented by daily treatment with small doses of cortisol or ACE. In contrast to intact animals, adrenalectomized rats exhibited markedly increased adrenocorticotrophic responses to mild stress. This pituitary hyperexcitability was not diminished by replacement therapy with corticoids alone but was considerably reduced by ascorbic acid given in conjunction with ACE. It is suggested that corticoids control the rate at which ACTH is synthesised in the pituitary gland and that other factors, including ascorbic acid, control the excitability of the pituitary gland in its adrenocorticotrophic response to stress.