Developmental expression of the epithelial na+ channel in kidney
and uroepithelia..
Watanabe, Shigeru, Kazumichi Matsushita, Paul B. McCray, Jr., and John
B. Stokes.
Laboratory of Epithelial Transport, Departments of Internal
Medicine and Pediatrics, University of Iowa, and the Veterans Affairs
Medical Center, Iowa City, IA 52242
APStracts 5:0210F, 1998.
The epithelial Na+ channel (ENaC) plays an important role in
regulating Na + balance in neonatal and adult life. Using in situ
hybridization, we localized [alpha]-, [beta]-, and [gamma]-rENaC mRNA
in developing rat kidney and uroepithelia. rENaC mRNA was first
detectable on fetal day 16 and by fetal day 17, mRNA was abundant in
the terminal collecting duct and uroepithelia. After birth, the
intensity of the signals for all 3 subunits increased in the cortical
collecting ducts and by 9 days after birth had diminished in the
inner medullary collecting ducts. Expression in uroepithelial cells
was different. [beta]-, and [gamma]-rENaC, but not [alpha]-rENaC mRNA
was detected in pelvis, ureters, and bladder at all stages of
development beyond fetal day 16. By RNase protection assay (RPA), the
greatest increase in subunit abundance in the kidney occurred before
birth. Between postnatal day 9 and 30, the abundance of [beta]- and
[gamma]-rENaC decreased relative to [alpha]-rENaC in outer and inner
medulla. The urinary bladder, in contrast, demonstrated the greatest
increase in [beta]- and [gamma]-rENaC mRNA abundance after birth. We
were generally unable to detect [alpha]-rENaC by RPA in urinary
bladder. Feeding weaned rats a diet of high or low NaCl did not
change the abundance of any of the subunit mRNAs in bladder. These
results demonstrate additional heterogeneity of developmental
expression and regulation of ENaC. The differences between the
collecting duct and uroepithelial cell rENaC mRNA regulation raise
the possibility of significant differences in function.
Received 4 May 1998; accepted in final form 24 November 1998.
APS Manuscript Number F103-8.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 9 December 1998