Twenty Wistar rats were nephrectomized unilaterally or sham-operated for the study of compensatory response of renal growth, including kidney weight, creatinine clearance (Ccr), and the role of insulin-like growth factor 1 (IGF-1). The remaining kidney weight had increased 26% above the control level on day 6, and 58% on day 28 after nephrectomy. The overall Ccr in rats with one functioning kidney was 75%, 88%, and 87% of the control values in two-kidney rats on days 1, 6, and 28, respectively after surgery. Serum IGF-1 concentrations were not different between the nephrectomy and sham groups. There was a nearly 2-fold increase in renal tissue IGF-1 concentration on day 6 in nephrectomized rats versus sham-operated controls (107.1 +/- 19.1 and 61.0 +/- 6.1 ng/g tissue, respectively), but no difference between the 2 groups on day 28 after surgery. Urinary IGF-1 excretion was found to be significantly elevated on day 6 after nephrectomy in association with high renal IGF-1 levels. This data suggests that renal IGF-1 production may be involved during the later phases of rapid compensatory renal growth.