The effect of endotoxemia on concanavalin A induced alterations in cytoplasmic free calcium in rat spleen cells as determined with Fluo-3.

The effects of acute (3 h) and chronic (30 h) in vivo infusions of Escherichia coli endotoxin on the Ca2+ homeostasis of rat spleen cells was investigated. Conditions were established for obtaining reliable estimates of Ca2+]i in these cells using the newly-developed Ca2+ indicator Fluo-3. The resting Ca2+]i of splenocytes and T lymphocyte-enriched preparations were 119 +/- 35 and 102 +/- 31 nM, respectively. Treatment of the cells with concanavalin A (Con A) resulted in a rapid increase in Ca2+]i. The magnitude of the increase was positively correlated with the concentration of Con A, whereas the time required to reach the maximum Ca2+]i was inversely related to the amount of Con A. The peak Ca2+]i was attained more rapidly in splenocytes (i.e. less than or equal to 30 s) than in the T cell-enriched fraction (i.e. 1.5-2.0 min). Both the resting Ca2+]i and the Con A-induced increase in Ca2+]i were similar to values previously reported for other lymphocyte cell types using different Ca2+ indicators, thereby supporting the values obtained with Fluo-3. Infusions of saline or endotoxin prior to the isolation of the cells did not result in significant alterations of either resting Ca2+]i or the cells' response to Con A. Since chronic infusions of endotoxin have previously been shown to cause a reduction in blastogenic responsiveness of splenocytes to Con A, these data suggest that the endotoxin-induced lesion occurs distal to the mobilization of intracellular Ca2+.