Effects of angiotensin II, ACTH, and KCl on the adrenal renin-angiotensin system in the rat

Angiotensin II, ACTH and potassium chloride were administered to rats for 6 days and the effects on adrenal renin-like activity and adrenal angiotensin II/III immunoreactivity were investigated. Rats infused with angiotensin II (140 pmol/min) either ip or sc showed increases in adrenal angiotensin II/III immunoreactivity (p less than 0.05) and plasma aldosterone concentration (p less than 0.05), but no change in adrenal renin-like activity. Captopril treatment of angiotensin II-infused rats caused a slight decrease in angiotensin II/III immunoreactivity which did not reach statistical significance. In contrast, rats treated with ACTH (Cortrosyn-Z, 3 IU/day, sc) showed an increase in adrenal renin-like activity (p less than 0.01), but no significant change in adrenal angiotensin II/III immunoreactivity. Rats treated with KCl in drinking water showed increases (p less than 0.05) in adrenal renin-like activity, adrenal angiotensin II/III immunoreactivity, and plasma aldosterone. These results suggest that angiotensin II, ACTH and potassium, three major regulators of aldosterone secretion by the adrenal gland, have different effects on the adrenal renin-angiotensin system when administered in vivo.