AREGU December 46/6

Choudhry, Mashkoor A., Philip E. Hockberger, and Mohammed M. Sayeed. PGE2 suppresses mitogen-induced Ca21 mobilization in T cells. Am. J. Physiol. 277 (Regulatory Integrative Comp. Physiol. 46): R1741–R1748, 1999.—PGE2mediated suppression of T cell proliferation during sepsis could result from altered Ca21 signaling. The present study evaluated the effects of PGE2 on Ca21 release from intracellular stores and its influx through the plasma membrane in splenic T cells from Sprague-Dawley rats. Intracellular Ca21 concentration ([Ca]i) responses in individual T cells were assessed using the Ca21 imaging technique, and the release of Ca21 from intracellular stores and Ca21 influx were spectrofluorometrically quantified in T cell suspensions. Under unstimulated conditions, nearly 85% of T cells exhibited [Ca]i #50 nM. After stimulation with concanavalin A (Con A), an increase in [Ca]i was recorded in ,60% of the cells. The pretreatment of T cells with PGE2 had no apparent effect on [Ca]i in resting cells; it significantly suppressed the Con A-induced increase in [Ca]i in all of the Con A-responsive cells. Ca21 release from the intracellular stores contributed to the early spike in [Ca]i, and the late phase of elevation in [Ca]i was dependent on Ca21 influx through the plasma membrane. Our data suggest that PGE2 causes an overall suppression of the Con A-induced [Ca]i elevation in T cells via inhibiting both Ca21 influx and its release from the intracellular stores.