title: In vitro studies on intestinal calcium and phosphate transport in horses.
abstract: Transepithelial transport mechanisms play a key role in regulating the absorption and secretion of calcium (Ca(2+)) and inorganic phosphate (P(i)) in the gastrointestinal tract. Although intestinal disorders with imbalances in macromineral homeostasis are frequently observed in horses, available data on intestinal Ca(2+) and P(i) transport are limited. The aim of the present study was to characterize the intestinal Ca(2+) and P(i) transport functionally by using the in vitro radioisotope tracer technique with Ussing chambers and to identify components involved in Ca(2+) transport at both mRNA and protein level. Among the different intestinal segments, the duodenum showed significant and highest active Ca(2+) absorption. The findings from RT-PCR and Western blot analysis suggest that the epithelial Ca(2+) channel TRPV6, the cytosolic calcium binding protein calbindin-D(9K) and the plasma membrane calcium ATPase PMCA may be involved in active transcellular Ca(2+) transport. Regarding the P(i) transport, the results indicate significant active P(i) secretion in the jejunum, but the contributing mechanisms remain unclear. A significant inhibiting effect of ouabain as an antagonist of the basolateral Na(+)/K(+)-ATPase on the serosal-to-mucosal P(i) transport suggests a pivotal role of Na(+) in jejunal P(i) transport in the horse.
authors: Department of Physiology, University of Veterinary Medicine Hannover, Foundation, Bischofsholer Damm 15, 30173 Hannover, Germany. anja.cehak@tiho-hannover.de
authors: Anja
authors: A
authors: Cehak
authors: Mirja R
authors: MR
authors: Wilkens
authors: Maria
authors: M
authors: Guschlbauer
authors: Nina
authors: N
authors: Mrochen
authors: Bernd
authors: B
authors: Schröder
authors: Karsten
authors: K
authors: Feige
authors: Gerhard
authors: G
authors: Breves
mesh_terms: D000818:Animals; D015153:Blotting, Western; D064026:Calbindins; D002118:Calcium / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics; D055724:Electrophysiological Phenomena / Q000187:drug effects; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D006736:Horses / Q000378:metabolism*; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism*; D007422:Intestines / Q000187:drug effects; D017136:Ion Transport / Q000187:drug effects; D049990:Membrane Transport Modulators / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D010710:Phosphates / Q000378:metabolism*; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D064030:S100 Calcium Binding Protein G / Q000235:genetics / Q000378:metabolism; D014700:Verapamil / Q000494:pharmacology
chemical_list: D064026:Calbindins; D018076:DNA, Complementary; D049990:Membrane Transport Modulators; D010710:Phosphates; D064030:S100 Calcium Binding Protein G; D010042:Ouabain; D014700:Verapamil; D053499:Plasma Membrane Calcium-Transporting ATPases; D002118:Calcium