IMMUNOHISTOCHEMICAL LOCALIZATION OF THE EPIDERMAL GROWTH-FACTOR, TRANSFORMING GROWTH-FACTOR-ALPHA, AND THEIR RECEPTOR IN THE HUMAN MESONEPHROS AND METANEPHROS

The distribution of epidermal growth factor (EGF), transforming growth factor cu (TGF alpha), and EGF/TGF alpha receptor were studied by mea ns of immunohistochemical methods starting from the very early stages of human embryonic kidney development. Mesonephros and metanephros wer e examined in order to detect immunoreactive staining in serial sectio ned embryos and fetal kidneys. Anti-EGF immunoprecipitates were found in the S-shaped mesonephric vesicles of g-week old embryos as well as in the mesonephric duct albeit with a lower degree of reactivity. Inte nse reactivity was observed in the metanephros within the blastemic ca ps of the same gestational period; the reaction was weaker within the ureteric bud branches. Bowmen's capsule, proximal tubules, and collect ing ducts were also reactive in the fetal kidney to varying degrees. T he distribution of TGF alpha reactivity in the mesonephros was similar to that observed for EGF but with a lower intensity. In contrast, the re was no reactivity in the metanephros, at least during the embyronic periods examined. By the 11th week of gestation, an intense reactivit y for TGF alpha polipeptide was shown in the fetal kidney at the level of the proximal tubules and Bowmen's capsule; distal tubules as well as all urinary structures from the collecting ducts to the pelvis were less reactive. Finally, EGF/TGF alpha receptor reactivity was identif ied by the 6th week of development, being more intense in the mesoneph ros at the level of the mesonephric duct cells. In the metanephros, th e ureteric bud-derived branches were reactive, whereas most of the bla stemic tissue did not stain. By the 11th week, only the collecting duc ts and the remaining urinary structures contained reaction products: R eactivity was distributed to the tissues originating from the ureteric bud branching. Taking into account recent advances in knowledge about the biology of growth factors, the hypothesis is proposed that the se cretory components (vesicles, glomerulus, and tubules) of renal anlage n might release the growth factors while the cells of the urinary trac t (i.e., collecting duct, pelvis, etc.) may be their targets. (C) 1996 Wiley-Liss, Inc.