EXPRESSION OF TGF-ALPHA, EGF AND THEIR COMMON RECEPTOR IN HUMAN FETALKIDNEY

Transforming growth factor-alpha (TGF-alpha) and epidermal growth fact or (EGF) are structurally related mitogenic polypeptides. They share t he same receptor; EGF receptor. The EGF receptor is widely expressed i n human fetal tissues including the kidney, but little is known about the role of TGF-alpha/EGF/ EGF receptor system in human fetal kidney. The expression of TGF-alpha, EGF and their common receptor was investi gated immunohistochemically in the human fetal kidneys. In the cortex, immunoreactivity for TGF-alpha was found in the differentiating proxi mal tubules. In contrast, immunoreactivity for EGF was present in the thick ascending limbs of the Henle's loop (TAL) and medullary collecti ng duct cells (CD). Immunoreactivity for their common receptor was pre sent: mainly in the TAL and medullary CD. These data support the assum ption that the system of TGF-alpha, EGF and its receptor has an import ant role in the proliferation and differentiation of the TAL and medul lary CD. The different localization of TGF-alpha and its receptor may indicate that TGF-alpha acts through a paracrine mechanism. The co-loc alization of EGF and its receptor in the TAL and medullary CD suggests that EGF may act as an autocrine growth factor.