Original Article

Effect of catecholamines on IL-2 production and NK cytotoxicity of rats in vitro

Yu-ping PENG, Yi-hua QIU, Jian-lan JIANG, Jian-jun WANG


To explore effects of exogenous and endogenous catecholamines on function of lymphocytes and primary mechanisms mediating the effects.
Splenocytes of rats were exposed to norepinephrine (NE), alpha- or beta-adrenoceptor antagonists plus NE, or alpha-methyl-p-tyrosine (alpha-MT), and then concanavalin A (Con A)-induced interleukin-2 (IL-2) production and natural killer (NK) cell cytotoxicity were determined by MTT assay and LDH assay, respectively.
Optical density (OD) values of NE-treated groups, which reflected IL-2 production, were 0.63, 0.61, and 0.60, respectively for 10(-10), 10(-9), and 10(-8) mol/L NE. They were all significantly reduced in comparison with control value of 0.68 (P<0.01). The effect of NE was blocked by either phentolamine (an alpha-adrenoceptor antagonist) or propanolol (a beta-adrenoceptor antagonist). OD values of alpha-MT, an inhibitor of tyrosine hydroxylase, at doses of 10(-10), 10(-9), and 10(-8) mol/L respectively were 0.71, 0.71, and 0.69, which were all notably higher than that of control (0.65, P<0.01). NK cytotoxicity was markedly attenuated by both NE and alpha-MT at the three doses mentioned above (17.69 %, 17.06 %, and 16.89 % versus 25.18 % for NE; 18.85 %, 18.44 %, and 17.04 % versus 23.22 % for alpha-MT; all P<0.01). The suppression of NK cytotoxicity by NE was prevented by propranolol but not by phentolamine.
Exogenous NE exerts a suppressive action in modulating functions of T and NK cells, with the former via both alpha- and beta-adrenoceptor mediated mechanisms and the later mainly through beta-adrenoceptors. Endogenous catecholamines synthesized by lymphocytes have also an autoregulatory effect on the lymphocytes themselves.

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