Effects of age at the time of unilateral nephrectomy and dietary protein on long-term renal function in rats.

Glomerular filtration rate (GFR) and urinary protein excretion (UpV) were studied in male rats with a uninephrectomy at 3 (UNX-3) or 15 weeks of age (UNX-15) and fed a low (12%, LP), normal (24%, NP) or high (36%, HP) protein diet. Measurements were made every 12 weeks throughout the entire life-span. The UNX rats were compared with sham-operated (2K) rats of the same age and on the same diets. At 12 weeks after surgery, the GFR of UNX rats, corrected for differences in body weight, age and protein intake (GFRcor), ranged between 73% and 77% of that of 2K rats. On the HP and NP diet, UpV was higher in UNX-3 than in UNX-15 rats. On the LP diet, UpV was equally low in both groups. Long-term follow-up indicated that the GFR of UNX rats on the HP diet started to decline first, followed by those on an NP diet, while those on an LP diet had the longest period of stable GFR. For UNX rats, the time to reach a GFRcor of 50% was used as an indicator of the length of renal survival. Analysis of variance of the renal survival times indicated a highly significant interaction between the protein diet and age at the time of UNX. On the HP diet, UNX-3 rats have a shorter renal survival time than UNX-15, while on the LP diet UNX-3 rats have a longer renal survival time. This indicates that the long-term outcome of UNX at young age depends on the protein intake.(ABSTRACT TRUNCATED AT 250 WORDS)