445 RENIN-ALDOSTERONE (R-A) RESPONSES IN A BOY WITH DEFECTIVE RENAL K+ EXCRETION

Abstract

Hyperkalemia and acidosis were found in an asymptomatic 1310/12 year old boy during evaluation of short stature and delayed adolescence (HA&BA=10 yrs). Renin activity was not evaluated in two similar reported cases. We studied the R-A system during changes in posture and diet to evaluate the effects of primary hyperkalemia. Hyperkalemic hyperchloremic metabolic acidosis was documented (Na 139,K 7.1,C1 116,CO2 19 mEq/1). Cortisol, thyroxine, GH and FSH/LH secretion were normal as well as inulin and PAH clearance. Urinary K+ excretion was low when compared to the elevated serum K+, both before and after Na2SO4 infusion. Plasma renin activity (PRA) was low(Na+120 mEq/day-supine(S) 0, upright(U) .06 ng/ml/hr). Although appropriate for normokalemic subjects, serum aldosterone was low for the degree of hyperkalemia(Na+120 mEq/day-S 18, U 39 ng/dl). During Na+ restriction PRA remained low, serum K+ rose to 8 mEq/1, and the patient became tachycardic and hypotensive. After chlorothiazide treatment, electrolyte abnormalities corrected and PRA increased(S 3.2, U 7.8 ng/ml/hr). Our studies support the hypothesis that renal K+ excretion is defective. These alterations in R-A responses may be attributed to the effects of hyperkalemia. Although it suppresses PRA, hyperkalemia directly increases aldo and thus partially compensates for decreased renin-angiotensin stimulation. We speculate that low PRA and resultant low angiotensin II caused decreased vascular tone, decreased Na+ retention and the patient's symptoms during Na+ restriction. CRC grant 5MO1RR42