Catecholamine responsiveness in human lymphocytes evaluated by intracellular free calcium measurements

Intracellular free calcium concentration [f(Ca2+)i] and cyclic adenosine monophosphate (cAMP) in lymphocytes and basal plasma noradrenaline (NA) were measured in nine healthy male subjects (age 22-72 years). Lymphocytes were stimulated with isoproterenol and the plant lectin concanavalin A (Con A). Con A induced a dose dependent increase in f(Ca2+)i without increasing inositol lipid turnover. The mechanism by which Con A mobilized f(Ca2+)i is not clear, but we found that the level of prostaglandin E2, a metabolite from arachidonic acid, increased after stimulation with Con A, indicating the possibility of arachidonic acid released by phospholipase A2. Isoproterenol inhibited the Con A-induced calcium mobilization in a dose dependent manner in lymphocytes stimulated with both isoproterenol and Con A. This inhibitory effect of isoproterenol is most probably mediated via cAMP. Both isoproterenol induced increase in cAMP and inhibition of calcium mobilization were significantly correlated to basal plasma NA. Taken together our data indicate that the lymphocyte response to a specific stimulus may depend not only on the strength of this stimulus, but also on the level of sympathetic nerve activity.