IMMUNOLOCALIZATION OF FIBROBLAST GROWTH-FACTOR-I AND GROWTH-FACTOR-2 IN THE EMBRYONIC RAT-KIDNEY

wFibroblast growth factors (FGF) regulate cell proliferation, migratio n, differentiation and angiogenesis during morphogenesis in many diffe rent tissues. Recent evidence indicates that exogenous FGF-2 stimulate s mesenchymal condensation in cultured rat metanephroi, a crucial epit helial-mesenchymal induction event in the developing nephron. The aim of the present investigation was to determine the in vivo distribution of FGF-1 and FGF-2 in developing rat metanephroi at embryonic days 14 , 15, 16, 18 and 20. Avidin-biotin enhanced indirect immunohistochemis try was used to demonstrate that both FGF-1 and FGF-2 were co-localize d in metanephroi at all ages studied. High levels of FGF-1 and FGF-2 w ere present in ureteric bud branches and in developing distal tubules. Fibroblast growth factor-1 and FGF-2 were colocalized in developing n ephron elements, from vesicles to S-shaped bodies, and in the mesangiu m of capillary loop and maturing stage glomeruli. Both growth factors were present in the mesenchyme of the nephrogenic zone and in the inte rstitium of the developing cortex. However, immunostaining for FGF was not evident in mesenchymal condensates, endothelial cells, medullary interstitial cells, or in the thin undifferentiated epithelium of the immature loop of Henle. These findings indicate that the expression of both FGF-1 and FGF-2 is tightly regulated in the embryonic kidney and suggest a role for these molecules in kidney development.