Improved dietary treatment with low protein and phosphorus restriction in uremic rats

The independent effect of low-protein or low-phosphorus diets in chronic renal failure were studied. The following four isocaloric diets, which contained various amounts of protein (24%, 6%) and phosphorus (0.5%, 0.12%) were fed to chronically uremic rats: high protein and no phosphorus restriction (HPrNP), high protein and phosphorus restriction (HPrRP), low protein and no phosphorus restriction (LPrNP), and low protein and phosphorus restriction (LPrRP). Adult male rats were made chronically uremic by electrocoagulation of one kidney and contralateral nephrectomy. Two grades of renal damage were produced, one of which was mild and the other severe. The mean number of days of survival in the severely uremic animals was 7.5 +/- (SEM) 2.5 with the HPrNP diet, 17.6 +/- 2.4 with the HPrRP diet, 20.3 +/- 2.3 with the LPrNP diet, and over 41.8 +/- 2.5 with the LPrRP diet during a 50-day period of observation. The BUN, serum creatinine (SCr), calcium (SCa), phosphorus (SP), urea and creatinine clearances (Curea, CCr), and plasma PTH levels before and 3 weeks after the diets were compared in the surviving rats with mild and severe uremia. There were marked reductions in the BUN and SP concentrations with the low-protein diets, whereas the SCa increased with all diets. Curea remained practically unchanged with the low-protein diets, whereas CCr decreased with all diets. Plasma PTH levels varied with each diet, but those rats with elevated PTH levels before dietary therapy experienced a fall in plasma PTH after the low-phosphorus diets were administered, with or without protein restriction.(ABSTRACT TRUNCATED AT 250 WORDS)