title: Accelerated calcium ion uptake in murine thymocytes induced by concanavalin A.
abstract: The mechanism of enhancement of Ca2+ uptake by the T cell mitogen concanavalin A (Con A) was studied in murine thymocytes. Native Con A enhanced the rate of Ca2+ uptake as much as 9-fold, an increase being observed within five minutes after Con A addition. The effect of Con A was reversed completely by alpha-methyl mannopyranoside (alpha-MM). Increased Ca2+ uptake was observed with increasing concentrations of Con A, between 2 and 400 microgram/ml, indicating that the stimulation of Ca2+ uptake is not restricted to mitogenic lectin concentrations (0.5-2 microgram/ml). Succinyl Con A exhibits only a slight effect in the same concentration ranges as native Con A. Ca2+ uptake, both in the absence and presence of Con A, is strongly dependent on energy metabolism and is carrier mediated. The augmentation of Ca2+ uptake by native Con A is due to an enhanced Vmax. Uptake of the anion, CrO42-, by thymocytes, found to be a non-saturable process, was also enhanced by Con A. The effect of Con A on CrO42- permeability appears to be independent of its effect on Ca2+ uptake.
mesh_terms: D001386:Azides / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002857:Chromium / Q000378:metabolism; D003208:Concanavalin A / Q000494:pharmacology*; D004140:Dinitrophenols / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D007700:Kinetics; D008766:Methylmannosides / Q000494:pharmacology; D013268:Stimulation, Chemical; D013601:T-Lymphocytes / Q000187:drug effects*
chemical_list: D001386:Azides; D004140:Dinitrophenols; D008766:Methylmannosides; D002857:Chromium; D003208:Concanavalin A; D002118:Calcium