Exchangeable sodium and renin in hypertensive diabetic patients with and without nephropathy

Abstract

The objective of this study was to examine total exchangeable sodium, plasma-blood volume, and the status of the renin-angiotensln system in hypertensive diabetic patients with established nephropathy. We also evaluated hypertensive patients with diabetes who were free of clinically apparent nephropathy or other diabetic complications. Total exchangeable sodium (by MNa dilution) was expressed as percentage predicted. Subjects were studied as inpatients receiving unrestricted sodium intake and in stable metabolic control. Total exchangeable sodium was 100 ± 2% in controls (n = 42), higher (p < 0.01) at 108 ± 2% in normotensive patients with diabetes (n = 30), and higher still (p < 0.005) in hypertensive patients with diabetic nephropathy (n = 16) 118 ± 4% (p < 0.05 vs normotensive diabetics). The value correlated with blood pressure only in diabetics with nephropathy (r = 0.61, p < 0.01). Plasma renin activity, and blood and plasma volumes were similar in nephropathic diabetics and controls. Hypertensive patients with maturity-onset (type II) diabetes free of nephropathy (n = 18) were compared with nondiabetic controls (n = 16) and normotensive patients with type II diabetes (n = 18) of similar age. Total exchangeable sodium in the controls was 100 ± 3%, higher (p < 0.01) in normotensive diabetics at 109 ± 2%, but not significantly elevated in hypertensive diabetics at 106 ± 2%. Again, blood and plasma volumes did not differ among the groups. Plasma renin activity was suppressed (p < 0.01) to a comparable degree in both normotensive and hypertensive patients with type II diabetes. Both sodium retention and the renin-angiotensin system may contribute to nephropathic diabetic hypertension. In nonnephropathic hypertension, sodium retention is not prominent and plasma renin activity is suppressed. © 1985 American Heart Association, Inc.