Document Detail

Taurine-conjugated bile acids act as Ca2+ ionophores.
MedLine Citation:
PMID:  1832296     Owner:  NLM     Status:  MEDLINE    
The ionophoretic properties of several taurine-conjugated bile acids have been investigated in two experimental systems: in a two-phase bulk partitioning system and in proteoliposomes. In the former, a bile acid/Ca2+ complex was extracted into the bulk organic phase and had an experimental stoichiometry of 1.75. Extraction was specific for Ca2+ over Mg2+; Na+ and K+ did not compete with the extraction of Ca2+. In the second system, bile acids at concentrations as low as 5-100 molecules/vesicle lowered the steady-state Ca2+ gradient maintained by a reconstituted sarcoplasmic reticulum Ca(2+)-ATPase. The effect was not due to nonspecific membrane perturbation. In addition to releasing intravesicular Ca2+ in a transmembraneous process, bile acids caused partition of Ca2+/bile acid complexes into the hydrophobic core of the bilayer. In both experimental systems, the Ca2+ ionophoretic activity correlated well with the concentration and the hydrophobicity of the bile acid. Taurolithocholate was most active, with a significant effect measurable at 10 microM in either system. Since bile acid concentrations equal to those used in our experiments can occur in the blood in certain liver diseases, the results support the notion that bile acids can increase the intracellular Ca2+ concentration bypassing the regulatory systems that maintain cellular Ca2+ homeostasis.
P Zimniak; J M Little; A Radominska; D G Oelberg; M S Anwer; R Lester
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Biochemistry     Volume:  30     ISSN:  0006-2960     ISO Abbreviation:  Biochemistry     Publication Date:  1991 Sep 
Date Detail:
Created Date:  1991-10-11     Completed Date:  1991-10-11     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  8598-604     Citation Subset:  IM    
Department of Internal Medicine, University of Arkansas for Medical Sciences, Little Rock 72205.
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MeSH Terms
Bile Acids and Salts / chemistry*,  pharmacology
Calcium / pharmacology*
Calcium-Transporting ATPases / chemistry
Chemistry, Physical
Ionophores / chemistry*,  pharmacology
Physicochemical Phenomena
Sarcoplasmic Reticulum / chemistry,  enzymology
Taurine / chemistry*,  pharmacology
Grant Support
Reg. No./Substance:
0/Bile Acids and Salts; 0/Ionophores; 0/Solutions; 107-35-7/Taurine; 7440-70-2/Calcium; EC ATPases

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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