The effect of synthetic angiotensin II on synthesis of aldosterone by the adrenals

Angiotensin II administered intravenously in doses of 40–50 μg./100g. body weight produced a significant increase in the capacity of the adrenal glands of rats to synthesize aldosterone. An increase in the production of corticosterone was not significant. The changes occurred about 24 hr. after the last injection of angiotensin, when the circulatory effects of the drug had ceased.

Since adrenocorticotrophic hormone (ACTH) with aldosteronotrophic activity, administered intravenously, did not result in increased steroid synthesis by the adrenals, it is unlikely that the phenomenon is due to mobilization of endogenous ACTH.

Angiotensin added to adrenal slices in vitro failed to produce the stimulating effect seen in vivo. Further investigations are needed to explain this difference.

Hypertension and renal loss of potassium

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The pineal gland and aldosterone

It has recently been suggested that the canine pineal gland secretes a hormone which stimulates the adrenal cortex to release aldosterone. The following experiments were undertaken to determine what effect pinealectomy or administration of bovine pineal extracts has on certain physiologic variables associated with aldosterone activity in rats: a) the relative size of the zona glomerulosa, compared with total adrenal area, was determined planimetrically in 25 female rats treated with pinealectomy, pineal extracts, or both; b) urinary potassium excretion was measured in 4 pinealectomized and 4 control female rats; c) the elective saline intakes, at concentrations ranging from 0 to 3.0%, were measured in 5 male control rats and in 5 animals given 1.0 ml/day of pineal extract. Pinealectomy or pineal extract had no effect on any of these variables, suggesting that the pineal gland does not regulate aldosterone secretion in the rat.

ALDOSTERONE METABOLISM IN LIVER DISEASE

Aldosterone secretion rates have been measured in six patients with cirrhosis of the liver using 16–3H aldosterone. The proportion of administered radioactivity excreted as pH 1 extractable conjugates and as a glucuronide has also been determined.

On unrestricted diets the aldosterone secretion rates were 19, 85 and 94 μg/day in three patients with ascites and oedema, and 140, 170 and 386 μg/day in three without fluid retention. Five of these patients were restudied after at least seven days on a low sodium diet (20 – 30 meq./day) and slight increases of secretion rate observed. The levels obtained were much lower than those previously reported for normal subjects on a low sodium diet. One patient was studied on a subsequent occasion after a haematemesis (urine sodium 1 meq./day), the secretion rate was 1130 μg/day.

The proportion of administered radioactivity excreted as glucuronide was below normal in at least one determination on four of the six patients and there was an increase of the proportion excreted as pH 1 extractable conjugates.

There was a striking variation of the proportion of radioactivity excreted as pH 1 extractable conjugates. One patient was studied on five occasions and the range was from 6.0 to 25.2 % of the administered radioactivity. This suggests that in patients with cirrhosis of the liver the urinary pH 1 extractable aldosterone may have a variable relationship to the actual secretion rate.