title: Trans- and paracellular calcium transport along the small and large intestine in horses.
abstract: Intestinal calcium absorption plays a key role in the maintenance of calcium homeostasis and may either occur by paracellular or transcellular mechanisms. The horse has some unique peculiarities in calcium homeostasis compared to other species including a high absorptive capacity for calcium in the intestine, high plasma calcium concentrations, high renal excretion, and low plasma concentrations of vitamin D metabolites. So far, knowledge about the underlying mechanisms and the regulation of intestinal calcium absorption is still limited concerning this species. Several studies have documented that intestinal calcium transport in horses is not as dependent on vitamin D as in other species. However, published data on other potential regulatory mechanisms are still lacking. In the present study, paracellular and transcellular transport mechanisms for intestinal calcium transport along the intestinal axis were identified in horses using the Ussing chamber technique. Furthermore, the expression of respective transport proteins including transient receptor potential vanilloid member 6, calbindin-D9kand calcium ATPase type 1 in line with the determined calcium flux rates was documented. In respect to regulation of transepithelial calcium transport, novel regulatory proteins for maintaining calcium homeostasis such as B-box and SPRY-domain containing protein and calmodulin were investigated for the first time in equine intestinal tissues in this study. This provides the basis for a new approach for a better understanding of equine calcium homeostasis regulation.
authors.affiliation: Department of Physiology, University of Veterinary Medicine Hannover, Foundation, Bischofsholer Damm 15, D-30173 Hannover, Germany.
authors.forename: M R
authors.initials: MR
authors.lastname: Wilkens
authors.affiliation: Department of Physiology, University of Veterinary Medicine Hannover, Foundation, Bischofsholer Damm 15, D-30173 Hannover, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Marholt
authors.affiliation: Department of Physiology, University of Veterinary Medicine Hannover, Foundation, Bischofsholer Damm 15, D-30173 Hannover, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Eigendorf
authors.affiliation: Department of Physiology, University of Veterinary Medicine Hannover, Foundation, Bischofsholer Damm 15, D-30173 Hannover, Germany.
authors.forename: A S
authors.initials: AS
authors.lastname: Muscher-Banse
authors.affiliation: Clinic for Horses, University of Veterinary Medicine Hannover, Foundation, Bünteweg 9, D-30559 Hannover, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Feige
authors.affiliation: Department of Physiology, University of Veterinary Medicine Hannover, Foundation, Bischofsholer Damm 15, D-30173 Hannover, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Schröder
authors.affiliation: Department of Physiology, University of Veterinary Medicine Hannover, Foundation, Bischofsholer Damm 15, D-30173 Hannover, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Breves
authors.affiliation: Department of Physiology, University of Veterinary Medicine Hannover, Foundation, Bischofsholer Damm 15, D-30173 Hannover, Germany. Electronic address: anjacehak@hotmail.com.
authors.forename: A
authors.initials: A
authors.lastname: Cehak
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005260:Female; D006736:Horses; D007420:Intestine, Large / Q000378:metabolism*; D007421:Intestine, Small / Q000378:metabolism*; D017136:Ion Transport; D008297:Male
chemical_list: D002118:Calcium
keywords: BSPRY; Calbindin-D(9k); Calmodulin; Horse; Intestinal calcium transport; Klotho; PMCA1; TRPV6