Excretion

Sodium

Plasma renin activity

Congenital adrenal hyperplasia

Endocrinology

Mineralocorticoid

Homeostasis

Organic chemistry

Blood pressure

Renin–angiotensin system

Aldosterone

Internal medicine

Fractional excretion of sodium

Medicine

Chemistry

Renal function

Pediatric Research

Na balance and fractional sodium excretion (FeNa) were measured in 10 infants with SLCAH, treated with subcutaneous pellets of 11-deoxycorticosterone acetate (DOCA). On 2mEqNa/Kg/d intake, Na balance was +.56 ± .30mEq/Kg/d (s.d.) n=10 and on 1 mEq/Kg/d + 0.05 ± .31 (n=18). On 1 mEqNa/Kg/d, FeNa decreased from 0.49 percent ± .08 (s.e.) to .23 + .02. Inexplicably, each infant showed an increase in plasma DOC on the lmEq/Kg diet: 170 + 18 (s.e.) ng/dl to 321 + 32 (P<.005). The correlation between changes in FeNa and DOC (r=-.155) was not significant and there was no significant change in blood pressure or creatinine clearance. Weight decreased 2.1 percent ± 0.6 (s.e.), but change in weight did not correlate with change in FeNa, DOC or plasma renin (PRA). Although PRA was elevated in many of these studies, there was no correlation between initial PRA and sodium excretion on day 3 of either diet. Maintaining Na balance on lmEq/Kg Na despite elevated initial PRA suggested that a compensation had been made to less than adequate DOC levels. One infant with congenital absence of adrenal function showed decrease in FeNa without a change in plasma DOC. Clearly DOCA therapy is necessary for sodium homeostasis in these mineralocorticoid deficient subjects. However, these data indicate that nonsteroidal mechanisms play a major role in the renal adjustment to acute Na restriction. (This work supported in part by USDA/SEA 58-7B30-9-60)

419 MECHANISMS OF SODIUM (Na) CONSERVATION IN SALT-LOSING CONGENITAL ADRENAL HYPERPLASIA (SL CAH)