Developmental expression of sodium entry pathways in rat
nephron.
Schmitt, Roland, David H. Ellison, Nicolette Farman, Bernard C.
Rossier, Robert F. Reilly, W. Brian Reeves, Ilse Oberb[umlaut]aumer,
Rosemarie Tapp and Sebastian Bachmann.
1Institut f[umlaut]ur Anatomie, Charit[acute]e, Humboldt
Universit[umlaut]at, D-10098 Berlin, Germany; 2University of Colorado
Health Sciences Center & VA Medical Center, Denver, CO; 3Institut de
Pharmacologie et de Toxicologie, Universit[acute]e de Lausanne, CH
-1002 Lausanne, Switzerland; 4University of Arkansas, Little Rock, AK;
and 5INSERM, Unit[acute]e 478, UER Xavier Bichat, F-75877 Paris Cedex
18, France
APStracts 5:0204F, 1998.
During the past several years, sites of expression of ion transport
proteins in tubules from adult kidneys have been described and
correlated with functional properties. Less information is available
concerning sites of expression during tubule morphogenesis, although
such expression patterns may be crucial to renal development. In the
current studies, patterns of renal axial differentiation were defined
by mapping the expression of sodium transport pathways during
nephrogenesis in the rat. Combined in situ hybridization and
immunohistochemistry were used to localize the Na-Pi cotransporter
type 2 (NaPi2), the bumetanide-sensitive Na-K-2Cl cotransporter
(NKCC2), the thiazide-sensitive Na-Cl cotransporter (NCC), the Na/Ca
exchanger (NaCa), the epithelial sodium channel (rENaC) and 11[beta]
-hydroxysteroid dehydrogenase (11HSD). The onset of expression of
these proteins began in post S-shape stages. NKCC2 was initially
expressed at the macula densa region and later extended into the
nascent ascending limb of the loop of Henle (TAL) while
differentiation of the proximal tubular part of the loop of Henle
showed a comparatively retarded onset when probed for NaPi2. The
thiazide-sensitive Na-Cl cotransporter was initially found at the
distal end of the nascent distal convoluted tubule (DCT) and later
extended towards the junction with the TAL. After a period of
changing proportions, subsegmentation of the DCT into a proximal part
expressing NCC alone and a distal part expressing NCC together with
NaCa was evident. Strong coexpression of rENaC and 11HSD was observed
in early nascent CNT and medullary collecting ducts, and later also
in the distal portion of the DCT. These data indicate that the
anatomical differentiation of the developing nephron generally
precedes expression of tubular transport proteins. Further, these
data obtained from the developing nephron may reconcile previous
observations concerning sites of ENaC expression by the inner
medullary collecting duct.
Received 6 August 1998; accepted in final form 13 November 1998.
APS Manuscript Number F195-8.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 20 November 1998