title: Intracellular free calcium concentrations in cell suspensions during hyperthermia.
abstract: The aim of this study was to explore the possibility that heat-induced alterations in calcium homeostasis are the cause of hyperthermic cell killing. Therefore, the intracellular free calcium concentration ([Ca2+]i) was determined spectrofluorometrically, using the fluorescent calcium probe fura-2/acetoxy methylester (AM), at both physiological and hyperthermic temperatures in cell suspensions from six different tumor cell lines. For all cell lines fura-2 leakage appears to contribute to a change in the fluorescence signal and hence leads to a false indication of an increase in [Ca2+]i, especially at the hyperthermic temperature. Two methods were introduced that circumvent this problem and results in true values of [Ca2+]i. Also, measurements of [Ca2+]i in single cells using a fluorescent microscopical technique (not affected by dye leakage) were used for comparison. All three approaches show that a hyperthermic treatment that kills > 90% of the cells does not lead to changes in the [Ca2+]i in most cell lines. Therefore, heat-induced alterations of calcium homeostasis cannot be considered the general cause for hyperthermic cell killing.
authors.affiliation: Department of Radiobiology, University of Groningen, The Netherlands.
authors.forename: P K
authors.initials: PK
authors.lastname: Wierenga
authors.forename: G J
authors.initials: GJ
authors.lastname: Stege
authors.forename: H H
authors.initials: HH
authors.lastname: Kampinga
authors.forename: A W
authors.initials: AW
authors.lastname: Konings
mesh_terms: D000818:Animals; D002118:Calcium / Q000032:analysis* / Q000378:metabolism; D002286:Carcinoma, Ehrlich Tumor / Q000737:chemistry* / Q000378:metabolism / Q000473:pathology*; D005334:Fever / Q000378:metabolism*; D007091:Image Processing, Computer-Assisted; D008223:Lymphoma / Q000737:chemistry* / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D008856:Microscopy, Fluorescence; D013050:Spectrometry, Fluorescence; D014407:Tumor Cells, Cultured
chemical_list: D002118:Calcium