Effect of epidermal growth factor on the developing rat renal papilla.
BACKGROUND
Apoptosis plays an important role in the morphogenesis of the renal papilla. During kidney development, ATL is derived from the TAL in the inner medulla by apoptotic deletion of a fraction of TAL cells and the transformation of the remaining TAL cells. EGF is an important regulator of apoptosis in the kidney.


OBJECTIVE
Exogenously administered EGF in postnatal rat affects renal papilla growth with cell proliferation and apoptosis in the loop of Henle.


METHODS
Rat pups received subcutaneous injections of EGF (0.3 microg/g body weight) or saline four times a day from after birth. Rats were sacrificed and the kidneys were preserved for immunohistochemistry on day 4 and day 7. The TAL was identified with antibody directed against Na-K-ATPase or BSC1, and type A intercalated cells were identified with antibody to anion exchanger 1 (AE1). Apoptosis was detected with TUNEL method, and cell proliferation with immunostaining for PCNA. RESULTS--PRIMARY AND SECONDARY: EGF treatment resulted in the following: (1) reduced kidney weight; (2) shortened length of renal papilla; (3) delayed transformation of the cuboidal epithelium into the squamous epithelium of the ATL; (4) delayed elimination of type A intercalated cells in the medullary collecting duct; (5) decreased both apoptotic index and PCNA-positive cells in the TAL and the collecting duct of the renal medulla.


CONCLUSIONS
These findings suggest that exogenous EGF delays the development of loop of Henle in the renal papilla by reducing both apoptosis and cell proliferation.
Lee
Seung-Hun
SH
Department of Internal Medicine, The Catholic University of Korea, Seoul, Korea.
Jung
Ju-Young
JY
Han
Ki-Hwan
KH
Yang
Chul-Woo
CW
Choi
Kyu-Bok
KB
Kim
Jin
J
D000818:Animals; D017209:Apoptosis; D002455:Cell Division; D004815:Epidermal Growth Factor / Q000502:physiology*; D020287:In Situ Nick-End Labeling; D007668:Kidney / Q000254:growth & development*; D008138:Loop of Henle / Q000166:cytology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D004815:Epidermal Growth Factor