Bile acids mobilise internal Ca2+ independently of external Ca2+ in rat hepatocytes.
In the present study, we investigated the possible role of external Ca2+ in the rise of the cytosolic Ca+ concentration induced by the monohydroxy bile acid taurolithocholate in isolated rat liver cells. The results showed that: (a) the bile acid promotes the same dose-dependent increase in the cytosolic Ca+ concentration (half-maximal effect at 23 microM) in hepatocytes incubated in the presence of 1.2 mM Ca2+ or 6 microM Ca2+; (b) taurolithocholate is able to activate the Ca2(+)-dependent glycogen phosphorylase a by 6.3-fold and 6.0-fold in high and low Ca2+ media, respectively; (c) [14C]taurolithocholate influx is not affected by external Ca2+, and 45Ca2+ influx is not altered by taurolithocholate. These results establish that the effects of taurolithocholate on cell Ca2+ do not require extracellular Ca2+ and are consistent with the view that monohydroxy bile acids primarily release Ca2+ from the endoplasmic reticulum in the liver.
Combettes
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Institut National de la Santé et de la Recherche Médicale, Unité de Recherche 274, Université Paris-Sud, France.
Berthon
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B
Doucet
E
E
Erlinger
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S
Claret
M
M
D000634:Aminoquinolines; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002132:Calcium Radioisotopes; D002478:Cells, Cultured; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D005260:Female; D005456:Fluorescent Dyes; D007700:Kinetics; D008095:Lithocholic Acid / Q000031:analogs & derivatives*; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D006005:Phosphorylases / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013656:Taurocholic Acid / Q000378:metabolism; D013658:Taurolithocholic Acid / Q000378:metabolism / Q000494:pharmacology*; D014667:Vasopressins / Q000494:pharmacology
D000634:Aminoquinolines; D002132:Calcium Radioisotopes; D005456:Fluorescent Dyes; D014667:Vasopressins; D013658:Taurolithocholic Acid; D013656:Taurocholic Acid; D008095:Lithocholic Acid; D006005:Phosphorylases; C035739:Quin2; D002118:Calcium