Postnatal development of carbonic anhydrase iv expression in rabbit
kidney.
Schwartz, George J., Jennifer Olson, Ann M. Kittelberger, Tohru
Matsumoto, Abdul Waheed and William S. Sly.
From the aDepartments of Pediatrics and Medicine, University of
Rochester School of Medicine, Rochester, NY 14642, and bDepartments
of Biochemistry and Molecular Biology, St. Louis University School of
Medicine, St. Louis, MO 63104.
APStracts 5:0212F, 1998.
Carbonic anhydrase (CA) IV activity facilitates renal acidification by
catalyzing the dehydration of luminal carbonic acid. CA IV has been
localized to the proximal tubules and medullary collecting ducts.
Maturation of CA IV expression has been considered to be important in
the development of renal acid excretion. The purpose of the present
study was to determine the maturational expression of CA IV in rabbit
kidney. A guinea pig polyclonal antibody to purified rabbit lung
microsomal membrane CA IV was generated. Immunoblotting of membrane
proteins after peptide-N-glycosidase F treatment revealed two N
-glycosylation sites and reduction in size from [sim]52 kDa to 35 kDa;
there appeared to be heavier glycosylation in the medulla. In
membrane and total proteins from the kidney cortex CA IV was 15-30%
of the adult level during the first two weeks of life, but increased
to mature levels by 5 weeks of age. The maturational pattern in the
cortex was confirmed by measuring SDS-resistant CA hydratase
activity. In the medulla both membrane and total proteins were
generally less than a quarter of the adult level of CA IV during the
first two weeks of life, before reaching mature levels by 5 weeks of
age. Immunohistochemistry showed staining in proximal tubules (apical
> basolateral) with maximal label in the S2 segment. CA IV also
appeared on the apical membranes of a minority cell type of the
cortical collecting duct, presumably the -intercalated cell. Several
labeled cells also appeared to be the process of being extruded from
medullary collecting ducts of 1-2 wk rabbits. The antibody did not
reliably detect medullary CA IV expression in sections from mature
rabbits. These studies indicate that there is a substantial postnatal
increase in expression of CA IV in the maturing kidney, both in
cortex and medulla. The disappearance of intercalated cells in the
maturing rabbit medullary collecting duct may be part of a normal
renal developmental program, as reported by Kim et al (Am. J.
Physiol. 270:F575, 1996). It is likely that the maturation of CA IV
expression contributes to the increase in renal acidification
observed early in postnatal life.
Received 27 March 1998; accepted in final form 25 November 1998.
APS Manuscript Number F076-8.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 9 December 1998