Spectrofluorimetric and image recordings of spontaneous and lectin-induced cytosolic calcium oscillations in Jurkat T cells.
Intracellular variations in Ca2+ concentrations have been measured in single Jurkat T lymphocyte variants (77 6.8 and E6.1) using Fura-2 as a probe. Under basal conditions, the cytosolic Ca2+ level is stable but some cells show spontaneous Ca2+ oscillations (frequency, 0.30 +/- 0.06 Hz). These oscillations are sensitive to the external concentration of Ca2+ since they can no longer be observed when the bathing solution is replaced (superfusion) with a Ca(2+)-free medium or when a Ca2+ chelator (EGTA) is added. Various changes in the cytosolic concentration of Ca2+ ([Ca2+]i) can be observed when the cells are exposed to the mitogenic lectin phytohemagglutinin (PHA, 80 nM). For instance, in the case of non-oscillating cells, the lectin induces either a rapid increase in [Ca2+]i that is followed by a sustained response (plateau) or it triggers Ca2+ spikes. In the case of experiments done in Ca(2+)-free medium, only the initial spike was observed. In the case of spontaneously oscillating cells, PHA induces a rapid increase in [Ca2+]i that is followed by a plateau where oscillations are absent. In every case, the PHA-dependent Ca2+ response is abrogated in a Ca(2+)-free medium. Computer simulations based on the model of Goldbeter et al. [27] show that the various Ca2+ responses of Jurkat cells are related to the cytosolic level of free Ca2+. Video imaging analyses show that the cellular Ca2+ responses are not homogeneous whether the observations are made in spontaneously oscillating Jurkat cells or when they are exposed to PHA.
Payet
M D
MD
Department of Physiology, Faculty of Medicine, University of Sherbrooke, Quebec, Canada.
Bilodeau
L
L
Héroux
J
J
Harbec
G
G
Dupuis
G
G
D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D003198:Computer Simulation; D003600:Cytosol / Q000378:metabolism; D006801:Humans; D007091:Image Processing, Computer-Assisted; D010835:Phytohemagglutinins / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D013601:T-Lymphocytes / Q000378:metabolism*; D014743:Videotape Recording
D010835:Phytohemagglutinins; D002118:Calcium