Effects of insulin on renal haemodynamics and sodium handling in normal subjects

Diabetic patients treated with insulin injected subcutaneously are characterized by peripheral hyperinsulinaemia and an increased mass of total body exchangeable sodium. We hypothesized that this may cause, at least in part, the glomerular hyperfiltration seen in the diabetic state. Six normal subjects were studied on 2 days in random order. Day A: Basal state for 40 min, hyperinsulinaemic eugly-caemic clamp for 1 h (insulin infusion rate 2 mU kg-' min-1 and 50% glucose infusion) and hyperinsulinaemic euglycaemic clamp combined with volume expansion (2 1 isotonic sodium chloride) for 2 h. Day B: as day A, but without insulin and glucose infusion.During combined volume expansion and hyperinsulinaemia an increase in glomerular filtration rate (GFR) (128± 6 vs 117 ± 8 ml min-1 1.73 m-2, p<0.01) and lithium clearance (CLi) (50 ± 4 vs 33 ± 5 ml min-1 1.73 m-2, p<0.01) was observed compared with basal conditions. GFR and CLi were unchanged during day B. Insulin infusion reduced renal sodium excretion. Absolute ...