Localization and regulation by vitamin d of calcium transport
proteins in rabbit cortical collecting system.
Baal, J[angstrom]argen Van, Alan Yu3, Anita Hartog, Jack A. M.
Fransen2, Peter H. G. M. Willems, Jonathan Lytton, and
Ren[circumflex]a J. M. Bindels.
Department of Cell Physiology, 1Biochemistry and Cell Biology,
University of Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The
Netherlands, Renal division, Dept. Medicine, Brigham and Women's
Hospital and Harvard Medical School, Boston MA 02115, U.S.A.,
Department of Medical Biochemistry, University of Calgary, Canada T2N
4N1
APStracts 3:0133F, 1996.
The 1,25[OH]2D3-induced expression of Na+-Ca2+ exchanger, Ca2+-ATPase
and calbindin-D28K, was investigated in the rabbit distal nephron.
Immunocytochemical studies in rabbit kidney sections revealed co
-localization of the three Ca2+ transport proteins in the majority of
cells in the distal nephron, including connecting tubules and
cortical collecting ducts. Subsequently, rabbit connecting and
cortical collecting tubule cells were immunodissected and cultured on
permeable supports. Immunocytochemical analysis of the cultured cells
by confocal microscopy revealed that Na+-Ca2+ exchanger and Ca2+
-ATPase were present at the basolateral membrane, whereas calbindin
-D28K was evenly distributed throughout the cytosol. Concomitant with
an increase in Ca2+ transport, 1,25[OH]2D3 increased calbindin-D28K
protein and RNA content 2- to 3-fold, as determined by Northern and
Western blotting. By contrast, neither Na+-Ca2+ exchanger nor Ca2+
-ATPase RNA or protein content were noticeably altered. Our findings
suggest that 1,25[OH]2D3 stimulation of transcellular Ca2+ transport
in primary cultures of rabbit cortical collecting system cells
involves an increase in the gene expression of calbindin-D28K, but
not of Na+-Ca2+ exchange and Ca2+ ATPase.
Received 22 January 1996; accepted in final form 18 July 1996.
APS Manuscript Number F26-6.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 4 August 1996