CATECHOLAMINE RESPONSIVENESS IN HUMAN-LYMPHOCYTES EVALUATED BY INTRACELLULAR FREE CALCIUM MEASUREMENTS

Intracellular free calcium concentration [f(Ca2+)(i)] and cyclic adeno sine monophosphate (cAMP) in lymphocytes and basal plasma noradrenalin e (NA) were measured in nine healthy male subjects (age 22-72 years). Lymphocytes were stimulated with isoproterenol and the plant lectin co ncanavalin A (Con A). Con A induced a dose dependent increase in f(Ca2 +)(i) without increasing inositol lipid turnover. The mechanism by whi ch Con A mobilized f(Ca2+)(i) is not clear, but we found that the leve l of prostaglandin E(2), a metabolite from arachidonic acid, increased after stimulation with-Con A, indicating the possibility of arachidon ic acid released by phospholipase A(2). Isoproterenol inhibited the Co n A-induced calcium mobilization in a dose dependent manner in lymphoc ytes stimulated with both isoproterenol and Con A. This inhibitory eff ect of isoproterenol is most probably mediated via cAMP. Both isoprote renol induced increase in cAMP and inhibition of calcium mobilization were significantly correlated to basal plasma NA. Taken together our d ata indicate that the lymphocyte response to a specific stimulus may d epend not only on the strength of this stimulus, but also on the level of sympathetic nerve activity.