EFFECT OF HYPERFILTRATION ON LONG-TERM FOLLOW-UP OF GLOMERULAR-FILTRATION RATE IN MALE WISTAR RATS

It has been suggested that a prolonged course of hyperfiltration could lead to progressive deterioration of renal function. In order to test this hypothesis, the following protocol was applied to 60 male Wistar rats. At 12 weeks of life, the rats were submitted to a surgical proc edure: sham operation (25 rats), unilateral nephrectomy (25 rats) or 3 /4 nephrectomy (10 rats). The three groups were again divided into two subgroups: one with high-protein intake (36%) and one with a low-prot ein intake (12%). In order to avoid any additional traumatic procedure which could shorten the animal's life, the glomerular filtration rate (GFR) was measured without blood sampling, using a previously validat ed technique based on an image recorded by a gamma camera between the 9th and the 10th min after intravenous injection of (99m)technetium di ethylenetriaminepentaacetate (DTPA). The sum of both kidneys and bladd er activity was expressed as a percentage of the injected dose. The te st was performed before surgery and every month thereafter. Six weeks after surgery, the highest filtration rate was found in the rats with ''two kidneys/high-protein diet'', followed by the ''two kidneys/low-p rotein diet'', the ''one kidney/high-protein diet'', the ''one kidney/ low-protein diet'' and the ''1/2 kidney''. The overall GFR in the one kidney/high-protein diet rat and in the 1/2 kidney rat was respectivel y 80% and 55% of the pre-operative values. Until 109 weeks of age, the survival rate was comparable in the five groups of rats. At 109 weeks of age, non-significant changes in renal function were observed, the follow-up slopes of the different subgroups being more or less paralle l. At that age, the lesions of glomerular sclerosis were focal and dis crete, without significant differences in the five groups.