Effect of graded renal ablation on kidney and serum insulin-like growth factor-I (IGF-I) and IGF binding proteins in rats: relation to compensatory renal growth.

Kidney insulin-like growth factor-I (IGF-I) increases transiently following unilateral nephrectomy, thus preceding the compensatory renal growth. The aim of the present study was to investigate the effect of different degrees (1/7 to 2/3) of renal ablation on kidney and serum IGF-I and IGF binding proteins (IGFBPs) during a 7-day study period. All nephrectomized rats exhibited an increase in the weight of the remaining renal tissue. Kidney IGF-I measured in kidney pieces close to and away from the resected area increased transiently and more significantly away from the resected area, with significant correlation to the amount of tissue resected (day 1, r = .73, P < .0001; day 2, r = .49, P < .05; and day 7, r = .48, P < .05). No changes in kidney IGFBPs or serum IGF-I were observed. Serum IGFBP-4 correlated to the degree of renal resection, as did changes in serum urea and creatinine. In conclusion, significant correlations were observed between local changes in kidney IGF-I and serum IGFBP-4 levels and the degree of renal ablation, suggesting a role for IGF-I as a renotropic factor and, further, that IGFBP-4 is removed to a major extent through the kidney.