Aims: To ascertain whether intravenous infusion of atrial natriuretic peptide (ANP) can induce microalbuminuria in patients with Type 1 diabetes mellitus (DM), as already demonstrated in patients with microalbuminuria, and to compare the albuminuric response to ANP infusion in Type 1 DM and a matched group of healthy non-diabetic controls.
Methods: Eight normoalbuminuric DM patients participated in a three limb, randomized, double-blind, placebo-controlled study. Subjects were kept euglycaemic by insulin infusion, and subsequently water-loaded (20 ml/kg orally plus urinary losses). When in steady state, a 30-min infusion of either placebo, ANP 0.025 mg x kg(-1).min(-1) or ANP 0.05 mg x kg(-1) x min(-1) was administered intravenously. Urine was collected every 15 min for 90 min for the estimation of albumin-creatinine ratio (ACR). In addition, eight nondiabetic volunteers received a single infusion of ANP 0.025 mg x kg(-1) x min(-1).
Results: ACR was unaltered by placebo in DM subjects (1.4 +/- 0.7-1.7 +/- 1.1 mg/mmol, mean +/- SD, ANOVA, P > 0.9), and by low dose ANP in controls (1.4 +/- 0.9-2.6 +/- 1.9 mg/mmol, P = 0.4). ACR increased with low dose ANP (1.3 +/- 0.5-14.6 +/- 13.6 mg/mmol, P = 0.02), and high dose ANP (1.3 +/- 0.7-26.4 +/- 31 mg/mmol, P = 0.01) in DM subjects. The ACR response to low dose ANP was greater in the DM than control subjects (P = 0.02).
Conclusions: ANP increases urine albumin excretion rate in normoalbuminuric Type 1 DM patients, and this effect is more pronounced than in healthy volunteers.