title: Duration of the calcium signal in the mitogenic stimulation of thymocytes.
abstract: An increase in the free cytoplasmic Ca2+ concentration in thymocytes can be detected by the fluorescent indicator quin 2 within a few seconds of the addition of concanavalin A and the response is quantified from the increased proportion of quin 2 in the cells chelated by Ca2+ ('% Ca-quin 2'). The % Ca-quin 2 in untreated cells is 53 +/- 6%, increases to 64 +/- 7% immediately after the addition of concanavalin A and declines spontaneously over 24 h back to the level in untreated cells (53 +/- 6%). The increase in % Ca-quin 2 in response to concanavalin A is completely blocked when 50 mM-alpha-methyl D-mannoside is added before concanavalin A and completely reversed when the competing sugar is added immediately after the mitogen. Addition of alpha-methyl D-mannoside at increasing intervals after concanavalin A addition causes a progressively smaller decrease in % Ca-quin 2 and has a negligible effect after 24 h, when the % Ca-quin 2 is the same as that in untreated cells. The decline in the calcium signal defined by these experiments has a similar time course to cap formation by concanavalin A on the cells. It is concluded that the calcium signal lasts only while concanavalin A is bound to the cell surface and is terminated either by capping or by the addition of alpha-methyl D-mannoside.
mesh_terms: D000634:Aminoquinolines; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003208:Concanavalin A / Q000494:pharmacology*; D005456:Fluorescent Dyes; D007152:Immunologic Capping; D037102:Lectins / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects; D008766:Methylmannosides / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D013050:Spectrometry, Fluorescence; D013601:T-Lymphocytes / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D014909:Wheat Germ Agglutinins
chemical_list: D000634:Aminoquinolines; D005456:Fluorescent Dyes; D037102:Lectins; D008766:Methylmannosides; D014909:Wheat Germ Agglutinins; D003208:Concanavalin A; C008466:methylmannoside; C035738:Quin2-acetoxymethyl ester; D002118:Calcium