EFFECTS OF PROLONGED INFUSIONS OF POTASSIUM CHLORIDE, ADRENOCORTICOTROPHIN OR ANGIOTENSIN II UPON SERUM ALDOSTERONE CONCENTRATION AND THE CONVERSION OF CORTICOSTERONE TO ALDOSTERONE IN RATS

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Abstract
The temporal relation between alterations in serum aldosterone [ALD] and in the conversion of labeled corticosterone [B] to ALD by incubated adrenal tissue was studied in conscious rats receiving long-term infusions of KCl, ACTH or angiotensin [A] II. When K-deficient rats were given KCl, a marked increase in serum ALD was observed only after 12 h, i.e., at a time when the conversion of B to ALD had become normal. After 24 h of ACTH infusion into Na- and K-replete rats the serum ALD was markedly elevated, whereas the conversion of B to ALD was significantly decreased. After 48 h of continued ACTH infusion the serum ALD returned to normal and there was a further decrease in the conversion rate. A 24 h A II infusion into Na- and K-replete rats induced significant increases in both the serum ALD and the conversion. After 48 h of continued A infusion the serum ALD returned to normal while the conversion and the blood pressure remained elevated. The activity of the enzymes involved in the final steps of ALD biosynthesis may become rate-limiting for the secretion of ALD during K deficiency and during prolonged ACTH treatment. The observed transiency of ALD stimulation by exogenous AII was not due to a suppression of the final steps of ALD biosynthesis and remains unexplained.