Subtotal nephrectomy: a mosaic of growth factors

We have studied the distribution of immunoreactive growth factors, by an avidin-biotin-peroxidase technique, throughout the course of progressive renal scarring in rats submitted to extensive renal ablation. Groups of rats (n = 6) were sacrificed at Days 7, 15, 21, 30, 90 and 150 following subtotal nephrectomy (SNx) by ligation and resection of the renal poles. During the early stages, when compensatory renal growth took place, increased renal immunostaining for insulin-like growth factor-I (IGF-I) and epidermal growth factor (EGF) was detected within the collecting ducts and distal tubules, respectively. As renal scarring became established by Days 90 and 150, these two growth factors were detected within the cells of damaged and vacuolated distal tubules. By contrast, a progressive increase immunostain for platelet-derived growth factor (PDGF)-AB was apparent within the glomeruli from Day 15 onward preceding the onset of glomerulosclerosis. A third staining pattern was apparent by Day 15 for transforming growth factor-beta (TGF-beta) and by Day 30 for IGF-I consisting of a perivascular and interstitial distribution coinciding with adventitial expansion and tubulo-interstitial fibrosis, respectively. A mosaic of growth factors is expressed within the kidneys of rats submitted to extensive renal ablation.