Corticosterone and aldosterone dose-dependent responses to ACTH and angiotensin II in the duck (Anas platyrhynchos).

The effects of [1-24]ACTH, [5-Val]angiotensin II, and potassium (K+) on the secretion of corticosterone and aldosterone by tissue slices from the subcapsular (SCZ) and inner (IZ) zones of the duck adrenal gland were determined using incubation and superfusion systems. Both methods demonstrated that the release of corticosterone and aldosterone from IZ and SCZ cells was dependent on the ACTH dose concentration. The IZ cells produced more corticosterone than the SCZ cells in response to stimulation with 1-1000 ng ACTH/ml. The dose response by aldosterone from the cells of the SCZ and the IZ were comparable, but the proportion of aldosterone per total amount of steroid released was greater by cells of the SCZ (11.3%), than by cells of the IZ (3.6%). Elevating the K+ concentration in the incubation medium from 4.0 to 6.5 and 11.2 mM did not directly stimulate corticosteroid release or potentiate the stimulatory effect of ACTH. Superfusion with 10(-12) to 10(-5) M AII stimulated the release of aldosterone from the SCZ cells but had no detectable effect on the IZ and failed to stimulate corticosterone release from either the SCZ or IZ cells. The results presented here demonstrate that in the bird stimulation for the release of corticosterone and aldosterone are different. Methodology for superfusion of adrenal tissue and for the direct radioimmunoassay of aldosterone and corticosterone in the superfusate are described.