Permissive role of calcium on regulatory volume decrease in freshly isolated mouse cholangiocytes.
Calcium (Ca2+) pathways are important in cell volume regulation in many cells, but its role in volume regulatory processes in cholangiocytes is unclear. Thus, we have investigated the role of Ca2+ in regulatory volume decrease (RVD) in cholangiocytes using freshly isolated bile duct cell clusters (BDCCs) from normal mouse. No significant increase in [Ca2+]i was observed during RVD, while ionomycin and ATP showed significant increases. Confocal imaging also showed no significant changes in the levels or distributions of intracellular Ca2+ during RVD. Cell volume study by quantitative videomicroscopy indicated that removal and chelation of extracellular Ca2+ by ethylene glycol-bis (beta-aminoethyl ether)-N,N,N-tetraacetic acid (EGTA) or administration of nifedipine did not affect RVD but verapamil significantly inhibited the RVD. Moreover, Ca2+ agonists or inhibitors of Ca2+ release from intracellular stores had no significant effect on RVD. However, 1,2-bis (2-aminophenoxy) ethane-N,N,N'N'-tetraacetic acid-AM (BAPTA-AM) showed significant decreases in [Ca2+]i and significantly inhibited RVD, which was reversed with coadministration of valinomycin, suggesting that BAPTA-AM-induced inhibition is due to potassium conductance or other cellular processes requiring permissive [Ca2+](i. These findings indicate that an increase in [Ca2+]i or extracellular Ca2+ is not required for RVD but Ca2+ has a permissive role in RVD of mouse cholangiocytes.
Park
Jae-Seung
JS
Department of Medicine, Division of Gastroenterology/Hepatology, Indiana University School of Medicine and Richard L Roudebush Veterans Affairs Medical Center, Indianapolis, IN 46202, USA.
Choi
Yong Jin
YJ
Siegrist
Vicki J
VJ
Ko
Yoo-Seung
YS
Cho
Won Kyoo
WK
D000818:Animals; D001653:Bile Ducts, Intrahepatic / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009543:Nifedipine / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014700:Verapamil / Q000494:pharmacology
D002121:Calcium Channel Blockers; D002614:Chelating Agents; D004533:Egtazic Acid; D014700:Verapamil; D009543:Nifedipine; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium