ABSTRACT
1. The effect of a 7-day low-protein diet on renal function was studied in 17 normotensive, normoalbuninuric, insulin-dependent diabetes (IDDM) patients. Glomerular filtration rate (GRF) and urinary albumin excretion (UAE) were measured after 7 days on an isocaloric low-protein diet (0.5g protein/Kg per day). 2. Compliance was confirmed by 24-h urinary urea levels, GFR was measured after a single injection of 51Cr-EDTA and UAE by radioimmunoassay. 3. GFR was reduced by 13.8% on the low-protein diet (139ñ 27.7 vs 120.4 ñ 25.1 ml min-1 (1.73m2) (P < 0.05). This effect was of the same magnitude as that obtained by others after long-term strict metabolic control. No changes were observed in UAE (5.6 ñ 6.4 vs 5.7 ñ 6.8 microng/min) during the study. The patients were classified as hyperfiltering (N = 9; GFR = 160.3 ñ 16.6 ml min-1(1.73m2)-1 or normofiltering (N = 8; 117.1 ñ 17.6 ml min-1(1.73m2)-1) on the basis of GFR, and no diference in the reduction of GFR was observed in either group. 4. The reduction in GFR is probably caused primarily by the reduction of protein intake since other factors that might influence the GFR such as glucose control and blood pressure did not change during the study