Sodium metabolism in insulin dependent diabetic patients. Role of insulin and atrial natriuretic peptide.

Acute insulin administration shows an antinatriuretic effect in normal man. Thus it can be postulated that insulin therapy resulting in circulating hyperinsulinemia can lead to sodium retention and in turn to hypertension in insulin dependent diabetes. Moreover it has been proved that atrial natriuretic peptide (ANP) plays a major role in modulating natriuresis in man. The aim of the present study was to investigate the relationship between insulin and ANP in modulating sodium metabolism in seven insulin dependent diabetic patients in comparison with eight normal control subjects at baseline and during a saline infusion (2 mmol/kg/90 min) at euglycemic blood levels. Diabetics received a subcutaneous insulin infusion (0.015 U/kg/hr) resulting in a two fold higher plasma free insulin levels (16 +/- 2 microU/ml) than in control subjects (7 +/- 2 microU/ml). During saline challenge sodium excretion rate increased by 29 +/- 6% in control patients and only by 6 +/- 0.7% in diabetic patients (p less than 0.01). At baseline ANP plasma concentrations were significantly higher in diabetic patients than in control subjects (diabetics = 37 +/- 8 pg/ml and controls = 21 +/- 3 (p less than 0.01). After saline challenge ANP concentration rose to 71 +/- 9 pg/ml in control subjects, whereas no significant change above baseline values was shown by diabetic patients.