Raised plasma concentrations of atrial natriuretic peptide (ANP) have been 
reported in patients with Type 1 (insulin dependent) diabetes mellitus (DM) who 
have poor glycaemic control and are associated with the presence of 
microalbuminuria. To test the hypothesis that elevations in plasma ANP 
concentration increase urinary albumin excretion in Type 1 DM, we have studied 
the effects of intravenous infusions of ANP in eight such subjects with 
established microalbuminuria. Blood glucose was maintained between 4 and 7 mmol 
l-1 in all subjects for the duration of studies; after euglycaemia had been 
established, a standard oral water load (20 ml kg-1 plus replacement of urinary 
losses) was given. Once steady state diuresis was attained, subjects received 
intravenous infusion of either placebo (0.9% saline), low dose (2.5 pmol kg-1 
min-1) or high dose (5.0 pmol kg-1 kg min-1) ANP solution in a randomized, 
double-blind protocol. Infusion of ANP caused a dose-dependent increase in 
urinary albumin excretion rate (placebo, 11.3 (SD 8.9) to 8.7 (SD 6.8) 
micrograms min-1; low dose ANP, 12.4 (SD 9.9) to 26.5 (SD 27.5) micrograms 
min-1, p < 0.01; high dose ANP 10.3 (SD 7.3) to 36.6 (SD 28.5) micrograms min-1, 
p < 0.001, ANOVA). Only high dose ANP caused an increase in urine flow. Blood 
glucose remained unchanged in all studies. We conclude that intravenous 
infusions of ANP cause a dose-dependent increase in urinary albumin excretion 
rate in Type 1 DM subjects with microalbuminuria. These data support the 
hypothesis that ANP has albuminuric actions which may contribute to 
microalbuminuria in Type 1 DM.