Basolateral store-operated Ca(2+)-entry in polarized human bronchial and colonic epithelial cells.
Bronchial epithelial cells respond to extracellular nucleotides from the luminal and basolateral side activating Cl- secretion via [Ca2+]i increase. In this study we investigated the differences of apically (ap) and basolaterally (bl) stimulated [Ca2+]i signals in polarized human bronchial epithelial cells (16HBE14o-). Specifically we investigated the localization of 'capacitative Ca2+ entry' (CCE). 16HBE14o- cells grown on permeable filters were mounted into an Ussing chamber built for the simultaneous measurement of Fura-2 fluorescence and electrical properties. Application of ATP from both sides induced a rapid [Ca2+]i increase and subsequent sustained [Ca2+]i plateau due to transmembraneous Ca(2+)-influx. The use of different nucleotides revealed the following rank order or potency which was very similar for addition from the apical or basolateral side: UTP (EC50 ap: 4 microM, bl: 5 microM) > ATP (EC50 ap: 4 microM, bl: 10 microM) > ADP (n = 4-7 from both sides). 2-MeS-ATP, AMP, adenosine and beta gamma-methylene ATP were ineffective (n = 3 from both sides). The ATP- (ap and bl) induced Ca2+ influx was only abolished by removal of basolateral Ca2+. This was also true for receptor-independent activation of Ca(2+)-influx by intracellular Ca(2+)-store depletion with 2,5 Di-(tert-butyl)-1,4-benzohydroquinone (BHQ) (10 microM). Also in polarized T84 cells the basolateral carbachol and BHQ activated Ca2+ plateau was exclusively sensitive to removal of basolateral Ca2+. We propose that in all polarized epithelial cells the CCE entry pathway is located in the basolateral membrane. We furthermore suggest that Ca2+[i elevating agonists acting from the apical side of the epithelium lead to the opening of a basolateral CCE pathway.
Kerstan
D
D
Physiologisches Institut, Albert-Ludwigs-Universität, Freiburg, Germany.
Thomas
J
J
Nitschke
R
R
Leipziger
J
J
D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D001980:Bronchi / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D004791:Enzyme Inhibitors; D006873:Hydroquinones; C019359:2,5-di-tert-butylhydroquinone; D000255:Adenosine Triphosphate; D002118:Calcium