EFFECTS OF INSULIN AND LIPID EMULSION ON RENAL HEMODYNAMICS AND RENALSODIUM HANDLING IN IDDM

To evaluate the role of insulin and hypertriglyceridaemia in the regul ation of renal haemodynamics and sodium handling in insulin-dependent diabetes mellitus (IDDM), 11 IDDM patients without microalbuminuria an d 13 weight-, age-, protein intake- and sex-matched healthy control su bjects were studied. Clearances of inulin (C-in), para-amino-hippuric acid (C-PAH), sodium (C-Na), and lithium (C-Li) were measured in four 60-min clearance periods (periods I, II, III and IV) during isoinsulin aemia with lipid emulsion infusion (study 1), a hyperinsulinaemic isog lycaemic clamp with Intralipid infusion (study 2), and during time-con trolled isoinsulinaemia (study 3). We found that C-in, C-PAH and filtr ation fraction were comparable in IDDM and control subjects, whereas C -Na was decreased in diabetic subjects (2.01 +/- 1.11 vs 3.03 +/- 1.32 ml/min; p < 0.05) due to elevations of proximal tubular fractional an d absolute reabsorptions of sodium (p < 0.05). Insulin infusion did no t affect C-in, increased C-PAH (p < 0.05) and, consequently, lowered t he filtration fraction (p < 0.01) in both groups. While acute hyperins ulinaemia resulted in increases in distal tubular fractional and absol ute reabsorptions of sodium (p < 0.01) contributing to a fall in C-Na (p < 0.01) in control subjects, in diabetic subjects the sodium-retain ing effect of insulin was not significant. The lipid emulsion did not alter any of the estimated parameters. We conclude that IDDM without m icroalbuminuria is associated with a tendency to sodium retention whic h is not aggravated by insulin when compared to control subjects. Acut ely induced hypertriglyceridaemia does not alter renal haemodynamics o r renal sodium handling.