Effects of steroidogenesis inhibition or stimulation on the catecholamine contents and on responsiveness of the cat adrenal medulla

Summary Adrenal catecholamine contents, adrenaline/noradrenaline ratio and secretory response of the perfused adrenal gland to DMPP were studied in cats following steroidogenesis inhibition by means of amino-glutethimide (alone or combined with betamethasone) or stimulation by means of ACTH plus ether inhalation. Administration of amino-glutethimide provoked an increase in adrenal weight, reduction in plasma and adrenal hydrocortisone and depletion of adrenal catecholamine without adrenaline/noradrenaline ratio change. When betamethasone was given together with amino-glutethimide, a further decrease in plasma and adrenal hydrocortisone was observed. On the contrary, adrenal weight increase was reduced and the adrenal catecholamine depletion was fully antagonized. Stimulation of the steroidogenesis by ether inhalation plus ACTH did not modify the adrenal catecholamine contents nor the adrenaline/noradrenaline ratio. In the amino-glutethimide plus betamethasone-treated animals, the adrenaline and noradrenaline output evoked by DMPP was not modified, as opposed to controls. On the contrary, the catecholamine output from glands of cats subjected to ether inhalation plus ACTH was significantly decreased. It is concluded that the inhibition or stimulation of the adrenal steroidogenesis does not modify the noradrenaline contents of the cat adrenal medulla and therefore noradrenaline is not merely a precursor for adrenaline. As a working hypothesis, it is suggested that the decrease in adrenal steroid secretion in the cortico-medullary portal system increases the chromaffin cell responsiveness, whereas an increase in steroid secretion decreases the chromaffin cell responsiveness.