title: Effects of calcium buffers and calbindin-D28k upon histamine-induced calcium oscillations and calcium waves in HeLa cells.
abstract: The effects of the artificial Ca(2+) buffers EGTA and BAPTA upon histamine-induced Ca(2+) oscillations and calcium waves were studied in HeLa cells. These events were also examined in HeLa cell lines transfected with the intracellular calcium-binding protein calbindin-D28k (CaBP; HeLa-CaBP) or the pCINeo vector alone (HeLa-pCINeo). High concentrations of the Ca(2+) indicators fluo-3 and fura-2 significantly influenced the oscillatory pattern of intracellular Ca(2+) in HeLa-pCINeo cells exposed to 1 microM histamine. Loading cells with low concentrations of the cell-permeant esters of the artificial Ca(2+)-buffers EGTA or BAPTA, resulted in fewer cells with a distinct "baseline" oscillatory pattern, and loading with higher concentrations of BAPTA almost completely abolished them. In HeLa-CaBP cells, stimulation with 1 microM histamine resulted in individual Ca(2+) spikes that had a flattened profile when compared to control cells; peak [Ca(2+)](i) was lowered, the rate of increase in [Ca(2+)](i) was slower and transients were prolonged. When compared to HeLa-pCINeo cells, loading with EGTA or BAPTA, or transfection of CaBP, significantly reduced the propagation velocity (by up to 60%) of Ca(2+) waves induced by exposure to 100 microM histamine. We conclude that intracellular Ca(2+) buffering exerts a significant influence on global Ca(2+) responses in HeLa cells and the propagation of Ca(2+) waves that underlie them. The relative effectiveness of different Ca(2+) buffers, including CaBP, appears to be particularly dependent upon the rapidity of their binding kinetics, with BAPTA being the most effective.
authors.affiliation: Department of Physiology, University of British Columbia, 2146 Health Sciences Mall, Vancouver, BC, Canada V6T 1Z3.
authors.forename: Gordon L
authors.initials: GL
authors.lastname: Rintoul
authors.forename: Kenneth G
authors.initials: KG
authors.lastname: Baimbridge
mesh_terms: D000814:Aniline Compounds / Q000494:pharmacology; D002021:Buffers; D064092:Calbindin 1; D064026:Calbindins; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects*; D002460:Cell Line; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D016257:Fura-2 / Q000494:pharmacology; D006367:HeLa Cells; D006632:Histamine / Q000494:pharmacology*; D006801:Humans; D064030:S100 Calcium Binding Protein G / Q000502:physiology*; D014162:Transfection; D014966:Xanthenes / Q000494:pharmacology
chemical_list: D000814:Aniline Compounds; D002021:Buffers; C576498:CALB1 protein, human; D064092:Calbindin 1; D064026:Calbindins; D064030:S100 Calcium Binding Protein G; D014966:Xanthenes; C059715:Fluo-3; D004533:Egtazic Acid; D006632:Histamine; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium; D016257:Fura-2