Inhibition of aldosterone production in diuretic-induced hyperaldosteronism by aldosterone antagonist canrenone in man

Suppression of surgical hyperaldosteronism by potassium canrenoate during gynecologic surgery under sevoflurane anesthesia

BACKGROUND

Surgical hyperaldosteronism leads to sodium and water retention during surgery and often causes postoperative edema. This study investigated the effect of potassium canrenoate (PC) on pituitary adrenocortical function in lower abdominal surgery under sevoflurane anesthesia.

METHODS

Twenty patients were randomized to receive 400 mg of PC (the PC group, n=10) or saline (the control group, n=10) intravenously. The following parameters were determined: plasma aldosterone, adrenocorticotropic hormone (ACTH), plasma renin activity (PRA), serum sodium and potassium, urinary sodium and potassium, and urine output.

RESULTS

The aldosterone and ACTH levels showed significant increases in the control group during surgery. Plasma ACTH also increased significantly in the PC group, but plasma aldosterone levels were unchanged during surgery. The urine Na/K ratio of the PC group was significantly higher than that of the control group.

CONCLUSION

The present study suggested that PC suppresses the increase of plasma aldosterone caused by surgical stress. That may prevent sodium retention and potassium excretion during surgery.

Relative inhibitory potency of five mineralocorticoid antagonists on aldosterone biosynthesis in vitro

Spirolactones are mineralocorticoid antagonists which bind to aldosterone receptors in the distal nephron. During the last decade, several antimineralocorticoids, which are more potent than spironolactone in competing for mineralocorticoid receptors have been developed. In the present study, we have compared the direct activity of spironolactone and four related compounds: prorénone (SC 23133), SC 19886, SC 26304 and its carboxylic analog SC 27169, on aldosterone biosynthesis. Two of them (SC 26304 and its carboxylic analog SC 27169) had no effect on adrenal steroidogenesis, even at concentrations up to 10(-3)M. Spironolactone and prorenone (SC 23133) induced a marked but reversible inhibition of aldosterone biosynthesis. SC 19886 totally inhibited aldosterone production and the activity of this compound lasted for more than 7 hours. In addition, SC 19886 and prorenone (SC 23133) totally suppressed ACTH and angiotensin II-induced stimulation of aldosterone biosynthesis whereas SC 27169 was unable to block adrenal response to these corticotropic hormones. Our results suggest that compounds such as prorenone (SC 23133), SC 19886 and spironolactone, which are potent inhibitors of aldosterone biosynthesis could be more active in the treatment of primary aldosteronism than those antimineralocorticoids which are devoid of action on aldosterone biosynthesis.

The effects of canrenoate K on corticosteroid biosynthesis in nephrectomized dogs

There is evidence from in vitro experiments that spironolactone not only antagonises the peripheral effects of aldosterone but also inhibits the production of corticosteroids by the adrenals. However relevant data from clinical studies are contradictory probably because spironolactone action on the kidneys also activates other mechanisms, such as renin secretion and potassium retention, which are potent stimulants of the adrenal cortex and thus tend to compensate for the inhibition. To determine the inhibitory effect of spironolactone on the adrenals in isolation, three groups of nephrectomized dogs were studied. Steroidogenesis was stimulated either by angiotensin II, potassium, or ACTH infusion. Potassium canrenoate was administered i.v. bolus at the beginning of the experiment. All the groups showed a similar marked decrease in plasma renin activity (PRA). Plasma aldosterone and cortisol were stimulated by the appropriate stimulus but their increase was blunted after the canrenoate K administration. The altered response between the subgroups was statistically significant (P less than 0.05). Plasma progesterone increased after the administration of canrenoate K. The response difference between the respective subgroups was again statistically significant (P less than 0.05). Canrenoate K was rapidly eliminated from the systemic circulation. These data indicate that canrenoate K causes a partial inhibition of aldosterone and cortisol stimulated secretion but augments the plasma levels of the precursor progesterone, as would be expected following inhibition of specific steps of corticosteroid biosynthesis.

The effect of the antimineralocorticoid RU 28318 on aldosterone biosynthesis in vitro

The effect of RU 28318, a specific and highly potent aldosterone antagonist on mineralocorticoid biosynthesis has been studied using a new in vitro model which combined three original features: (1) a very specific radioimmunoassay for aldosterone (2) a simplified perifusion system and (3) frog interrenal tissue which spontaneously produces high amounts of aldosterone. A dose-related inhibition of aldosterone production was observed for doses ranging from 10(-5) to 10(-3) M of RU 28318. The intermediate dose of 10(-4) M caused 71% inhibition of aldosterone production. Long term infusion of RU 28318 for 8 h led to a significant, stable and reversible inhibition of aldosterone production. In addition, we provide evidence that RU 28318 is capable of blocking the stimulation of aldosterone secretion induced by synthetic ACTH or by angiotensin II analogue. The present results demonstrate that RU 28318 is responsible for a significant and reversible inhibition of spontaneous, ACTH-induced and angiotensin II-induced aldosterone biosynthesis in vitro.

Spironolactone in thiazide-induced hypokalaemia: variable response between patients

1 The influence of spironolactone 25, 50, 100 and 200 mg daily, and placebo, on plasma potassium and other variables was examined in a random crossover study of 15 hypertensive patients taking bendrofluazide 10 mg daily. 2 Spironolactone produced significant dose-related increases in plasma potassium and aldosterone, and reductions in plasma sodium and bicarbonate. 3 In 14 compliant patients plasma concentrations of the major metabolite canrenone were related linearly to the dose of spironolactone, and there was less than twofold variation between patients. The plasma canrenone concentration correlated negatively with body weight (r = -0.77, P less than 0.001). 4 The plasma potassium response to spironolactone varied sevenfold between compliant patients. The response correlated negatively with placebo plasma potassium (r = -0.62, P less than 0.02), positively with plasma canrenone (r = +0.55, P less than 0.05), but was unrelated to plasma aldosterone (r = -0.22). In one patient relative resistance to spironolactone was attributed to exaggerated secondary hyperaldosteronism induced by the drug. 5 The variability in response to spironolactone between patients is such that fixed dose thiazide-spironolactone combination tablets are unlikely to prevent hypokalaemia reliably.

Canrenoate disposition in dogs. Tissue distribution and elimination

The metabolism and tissue distribution of intravenously administered C14-canrenoate-potassium (CR-K) was studied at various time intervals in 10 dogs. After a rapid decline of total radioactivity immediately after injection, the elimination in plasma occurred in two distinct phases with half-lives of 6.8 and 23.6 h. Canrenoate was rapidly converted to lipid- and water-soluble metabolites which were separated by thin-layer chromatography. Most tissues showed similar concentrations of total radioactivity as plasma. An accumulation of radioactivity per g wet weight was detected in the adrenal glands and fat tissue as well as in the metabolic and excretory organs but not in the heart. Taking into consideration that skeletal muscle, fat tissue and liver constitute about 64% of the body weight, it is obvious that the main part of total radioactivity was present in these tissues. In contrast to plasma, urine and feces, where various metabolites could be analysed, the bulk of radioactivity in tissues is represented by canrenone. Thus, the estimation of the parent compound and its metabolites in plasma, urine and feces does not allow final conclusions about the active substance in various tissues. Within 72 h 47% of the dose was recovered in urine and 49% in feces.

Change in antikaliuretic response to potassium-sparing diuretics in patients with cirrhotic ascites

In 2 elderly patients with ascites due to hepatic cirrhosis, potassium excretion decreased during re-administration of potassium-sparing diuretics after recurrence of ascites following withdrawal of previous prolonged treatment. An exaggerated antikaliuretic response and a paradoxic rise in potassium excretion are "unpredictable" changes which may occur during administration of potassium-sparing diuretics at different times in the same patient treated with the same drug.

Effect of aldosterone antagonist canrenone on plasma aldosterone concentration and plasma renin activity, and on the excretion of aldosterone and electrolytes by man

Canrenone was administered in doses of 2 x 82 mg and 2 x 164 mg per day over a period of 10 days to diabetic patients without cardiovascular, liver or kidney involvement. Aldosterone excretion and plasma aldosterone increased only slightly during both regimes. There was a clear-cut increase in aldosterone excretion only after discontinuation of canrenone. Excretion of sodium, potassium and fluid was not significantly changed either during or after treatment. The lack of effect of canrenone on the kidney was in contrast to the significant decrease in serum sodium and increase in serum potassium, and the significant, dose-dependent rise in plasma renin activity following canrenone administration. The increased plasma renin activity persisted for some days after discontinuation of canrenone. It is suggested that canrenone primarily exerted its effect in the distal part of the large intestine where ionic movements are most affected by aldosterone. The disproportionately slight increase in plasma aldosterone concentration and aldosterone excretion, in spite of the greatly elevated plasma renin activity and serum potassium level, is considered to be due to a direct inhibitory effect of canrenone on aldosterone production in the adrenals.