Open AccessCalcium transport in bovine rumen epithelium as affected by luminal Ca concentrations and Ca sources
Author(s) -
Schröder Bernd,
Wilkens Mirja R.,
Ricken Gundula E.,
LeonhardMarek Sabine,
Fraser David R.,
Breves Gerhard
Publication year - 2015
Publication title -
physiological reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 39
ISSN - 2051-817X
DOI - 10.14814/phy2.12615
Subject(s) - rumen , propionate , calcium , chemistry , ion transporter , ussing chamber , absorption (acoustics) , flux (metallurgy) , calcium metabolism , in vitro , biochemistry , biophysics , biology , membrane , fermentation , physics , organic chemistry , acoustics
Abstract The quantitative role of different segments of the gastrointestinal tract for Ca absorption, the respective mechanisms, and their regulation are not fully identified for ruminants, that is, cattle. In different in vitro experiments the forestomach wall has been demonstrated to be a major site for active Ca absorption in sheep and goats. In order to further clarify the role of the bovine rumen for Ca transport with special attention to luminal Ca concentrations, its ionic form, and pH , electrophysiological and unidirectional flux rate measurements were performed with isolated bovine rumen epithelial tissues. For Ca flux studies ( J ms , J sm ) in vitro Ussing chamber technique was applied. Standard RT ‐ PCR method was used to characterize TRPV 6 and PMCA 1 as potential contributors to transepithelial active Ca transport. At Ca concentrations of 1.2 mmol L −1 on both sides of the tissues, J ms were higher than J sm resulting under some conditions in significant Ca net flux rates ( J net ), indicating the presence of active Ca transport. In the absence of an electrical gradient, J net could significantly be stimulated in the presence of luminal short‐chain fatty acids ( SCFA s). Increasing the luminal Ca concentrations up to 11.2 mmol L −1 resulted in significant increases in J ms without influencing J sm . Providing Ca in its form as respective chloride, formate, or propionate salts there was no significant effect on J ms . No transcripts specific for Ca channel TRPV 6 could be demonstrated. Our results indicate different mechanisms for Ca absorption in bovine rumen as compared with those usually described for the small intestines.