Dietary protein and insulin-like growth factor-I content following unilateral nephrectomy

The compensatory renal growth (CRG) that follows unilateral nephrectomy (UNx) in the rat is blunted by a low protein diet (LPD). CRG in rats is associated with a parallel increase in insulin-like growth factor (IGF)-I/somatomedin-C content of the kidney. In this study, we have examined the effects of dietary protein manipulations on IGF-I and -II within remaining kidneys of rats during CRG following UNx. Adult Wistar rats were given a LPD (8% wt/wt casein), medium protein diet (MPD, 18%), or high protein diet (HPD, 78%) for 30 days prior to surgery. At surgery, either a right UNx or a sham operation was performed. Four days later, animals were sacrificed. Kidney weight, protein, DNA, IGF-I and -II contents were measured. Serum and hepatic content of IGF-I were also measured. CRG (%) was calculated comparing kidney weights pre- and post-UNx and between UNx and sham operated rats at sacrifice. At sacrifice, kidney weight was proportional to dietary protein intake in sham and UNx rats. Fractional kidney wt was significantly increased in UNx rats on each of the three diets compared to sham operated animals (P less than 0.001), but was greater in rats on HPD (35%) compared to those on MPD (23%) or LPD (20%). CRG was minimal on LPD (9.6 +/- 6.8%), compared to MPD (23.8 +/- 9.6%) and HPD (43.8 +/- 25.4%). The mean kidney content of IGF-I did not differ between dietary groups in sham operated rats.(ABSTRACT TRUNCATED AT 250 WORDS)