Plasma renin activity in insulin-dependent diabetics with raised glomerular filtration rate

Basal and ambulant plasma renin activity (PRA) were measured in 12 insulin-dependent diabetics (IDDS) with elevated glomerular filtration rate (GFR), 12 IDDs with normal GFR matched for age, sex and duration of diabetes and 12 age and sex matched non-diabetic control subjects. The two diabetic groups did not differ with respect to extracellular fluid volume, urinary sodium excretion, arterial blood pressure, mean plasma glucose concentration or urinary glucose excretion. Basal PRA did not differ significantly between the three groups. Ambulant PRA was significantly higher (P less than 0.02) in the group of IDDs with elevated GFR than in the control group. Our data suggest that, in IDDs with high GFR, haemodynamic alterations may stimulate a rise in PRA and thus angiotensin, a potent vasoconstrictor. Whether this represents an attempt of the renin-angiotensin system to normalise GFR or is the result of insensitivity of the renal vasculature to circulating angiotensin remains to be established.