Plasma aldosterone (PA) and plasma renin activity (PRA) were determined in 44 diabetics, of whom nine were normotensive but not nephropathic (group 1), 10 were hypertensive but not nephropathic (group 2), and 25 were hypertensive and nephropathic (group 3); they were kept in balance on a diet composed of 10 to 20 mEq. of sodium (Na) and 100 mEq. of potassium (K). Supine PA in group 1 was 38 ± 7 ng. per deciliter, whereas in normals it was 24 ± 2 ng. per deciliter (P < 0.05); beyond that, neither supine nor upright PA or PRA differed significantly from normal in groups 1 and 2. By contrast, in group 3, supine PA was 13 ± 1 ng. per deciliter and PRA 2.0 ± 0.2 ng./ml. and upright PA was 39 ± 7 ng. per deciliter and PRA 3.8 ± 0.5 ng./ml., all significantly lower than those in the other groups (P < 0.01). Nine patients, one in group 1 and eight in group 3, had low supine and upright PA and PRA; four had hyperkalemia. An additional nine patients in group 3 had low upright PA, with normal or low PRA; two had hyperkalemia. Of the 18 patients with low upright PA, K correlated with glucose (R = 0.46, P < 0.05). These results suggest (1) the renin-aldosterone system generally responds normally in diabetics without nephropathy but responds subnormally when nephropathy is present, (2) hyporeninemic hypoaldosteronism is frequent in diabetics with nephropathy but may occur in the absence of clinical nephropathy, and (3) hyperkalemia in some diabetic patients may be secondary to hypoaldosteronemia and hyperglycemia.

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