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A 9-year-old boy who complained of fatigue, myalgias, and progressive weakness was found to have a markedly elevated serum creatine phosphokinase (CPK). He developed polyuria with polydipsia and was noted to be hypertensive and severely hypokalemic. Treatment with potassium and spironolactone alleviated his signs and symptoms and normalized the blood pressure and CPK. Initial studies revealed low plasma renin activity that did not increase with change from supine to upright position. Plasma aldosterone was consistently elevated in the supine position, decreased with upright posture, and was not suppressed by administration of dexamethasone. Plasma 18-hydroxycorticosterone also was elevated. Enhanced computerized tomography (CT) revealed a mass in the left adrenal that had not been seen on the initial unenhanced scan. Adrenal vein catheterization confirmed elevated plasma aldosterone on that side. Adrenalectomy was performed, and a well-encapsulated adenoma was found at examination of the surgical specimen. Postoperatively, suppression of plasma renin activity continued for many months without signs of aldosterone deficiency.

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Inactive renin has been isolated from pooled amniotic fluid and purified approximately 642-fold. Prior to activation the isolates had approximately 4% of the activity found after activation. The observation is similar to that reported for inactive renin from chorionic cell culture and suggests a placental origin of amniotic fluid inactive renin. Using plasma from an estrogen-treated woman, renin substrate was recovered free of renin and inactive renin and a portion was separated into NMW and HMW components. The NMW form constituted approximately 93% and the HMW form approximately 7% of the renin substrate. Amniotic fluid inactive renin was used for determinations of enzyme-substrate kinetics with the pooled, NMW, and HMW plasma substrate and tetradecapeptide synthetic substrate, and the results were compared to similar determinations using standard renal renin. Using synthetic substrate, the kinetics of renal renin and amniotic fluid inactive renin before and after activation were similar. The kinetics of renal renin with pooled, NMW, and HMW plasma substrate were also similar. Amniotic fluid inactive renin had a lower Km with pooled than with NMW substrate, however, which resulted from a significantly smaller Km with HMW component. Although the affinity constants with pooled substrate were not different for renin and inactive renin, the Km of inactive renin was significantly less with the HMW component of plasma renin substrate. The observations are compatible with a role for placental inactive renin in normal pregnancy and suggest the possibility of a further role in hypertensive pregnancy.

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1. Inactive renin was isolated from human amniotic fluid by chromatography with DEAE-cellulose, pepstatin-aminobutyl-agarose, octylagarose and Cibacron Blue F3GA columns. 2. Before and after isolation from amniotic fluid, inactive renin could be activated by incubation with pepsin and by dialysis to pH 3.3, and the acid activation could be reversed by subsequent incubation at pH 7.4 and 37 degrees C. 3. Inactive renin was not activated by procedures expected to dissociate renin from an inhibitor. 4. The results suggest a pH-dependent conformational change as the mechanism of reversible acid activation of inactive renin in amniotic fluid. 5. There are chromatographic and activation similarities of inactive renin from human plasma, kidney and amniotic fluid.

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An infant with severe neonatal hyponatremia and hyperkalemia is described. Although marked elevations of urinary 17-hydroxycorticosteroids suggested an 18-dehydrogenase aldosterone biosynthetic defect, the infant proved to have mineralocorticoid unresponsiveness, or pseudohypoaldosteronism. Dietary sodium supplementation and ion exchange resin administration resulted in normalization of serum electrolytes and urinary 17-hydroxycorticosteroids. ACTH infusion produced natriuresis, suggesting the need for additional sodium supplementation during the stress of illness, with a resultant increase in ACTH secretion. Determinations of the relative amounts of urinary 18-hydroxy and aldosterone metabolites appear necessary for early definitive diagnosis of the disorder.

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Plasma renin activity (PRA) and the concentrations of renin (PRC) and big renin (PBRC) have been determined in maternal and fetal blood, and renin and big renin have been measured in amniotic fluid, at 16 to 20 weeks of gestation. Gradients between peripheral arterial and venous and uterine venous maternal circulation were not apparent for PRA, PRC, or PBRC. PRC and PBRC but not PRA were consistently higher in fetal cord blood than in the maternal compartment. The concentrations of big renin and of renin were tenfold higher in amniotic fluid than in maternal plasma and were significantly correlated in amniotic fluid but not maternal or fetal plasma.

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The response of endogenous angiotensin II levels to positional change, lateral to supine recumbency, was investigated in a prospective study of 55 primigravid patients during the last half of pregnancy. Blood samples were obtained in the lateral and supine recumbent positions. The mean supine angiotensin II level was significantly higher between 29 and 34 weeks' gestation in those patients destined to develop pregnancy-induced hypertension than in those who remained normotensive (P less than 0.05). As gestation advanced, the mean per cent relative change of angiotensin II from the lateral to the supine position altered from negative to positive in those patients destined to develop pregnancy-induced hypertension, whereas it remained negative in those patients who remained normotensive. These findings are discussed in relation to pathophysiologic alterations in the development of pregnancy-induced hypertension.

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A 6-year-old girl with lymphosarcoma developed Cushing's syndrome. Suppression-stimulation studies verified adrenal hyperfunction secondary to bilateral adrenocortical hyperplasia, and the course suggested the possibility of "ectopic ACTH" production by the neoplasm as the etiology.

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