Title: Duodenal calcium absorption in vitamin D receptor-knockout mice: Functional and molecular aspects
Authors: Van Cromphaut, Sophie
Dewerchin, Mieke
Hoenderop, JGJ
Stockmans, Ingrid
Van Herck, Erik
Kato, S
Bindels, RJM
Collen, Desire
Carmeliet, Peter
Bouillon, Roger
Carmeliet, Geert # ×
Issue Date: Nov-2001
Publisher: Natl acad sciences
Series Title: Proceedings of the National Academy of Sciences of the United States of America vol:98 issue:23 pages:13324-13329
Abstract: Rickets and hyperparathyroidism caused by a defective vitamin D receptor (VDR) can be prevented in humans and animals by high calcium intake, suggesting that intestinal calcium absorption is critical for 1,25(OH)(2) vitamin D [1,25(OH)(2)D-3] action on calcium homeostasis. We assessed the rate of serum Ca-45 accumulation within 10 min of oral gavage in two strains of VDR-knockout (KO) mice (Leuven and Tokyo KO) and observed a 3-fold lower area under the curve in both KO strains. Moreover, we evaluated the expression of intestinal candidate genes involved in transcellular calcium transport. The calcium transport protein1 (CaT1) was more abundantly expressed at mRNA level than the epithelial calcium channel (ECaC) in duodenum, but both were considerably reduced (CaT1 > 90%, ECaC > 60%) in the two VDR-KO strains on a normal calcium diet. Calbindin-D-9K expression was decreased only in the Tokyo KO, whereas plasma membrane calcium ATPase (PMCA(1b)) expression was normal in both VDR-KOs. In Leuven wild-type mice, a high calcium diet inhibited (> 90%) and 1,25(OH)(2)D-3 injection or low calcium diet induced (6-fold) duodenal CaT1 expression and, to a lesser degree, ECaC and calbindin-D-9K expression. In Leuven KO mice, however, high or low calcium intake decreased calbindin-D-9K and PMCA1b expression, whereas CaT1 and ECaC expression remained consistently low on any diet. These results suggest that the expression of the novel duodenal epithelial calcium channels (in particular CaT1) is strongly vitamin D-dependent, and that calcium influx, probably interacting with calbinDin-D-9K, should be considered as a rate-limiting step in the process of vitamin D-dependent active calcium absorption.
ISSN: 0027-8424
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Clinical and Experimental Endocrinology
Laboratory of Intensive Care Medicine
Vesalius Research Centre (-)
Molecular and Vascular Biology
Laboratory of Angiogenesis and Vascular Metabolism (Vesalius Research Center) (+)
× corresponding author
# (joint) last author

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