MECHANISTIC DIFFERENCES IN NK CELL CYTOLYTIC ACTIVITY IN TREADMILL-TRAINED AND CHRONIC ETHANOL-CONSUMING MICE

The present study was undertaken to investigate mechanisms contributin g to differences in natural killer (NK) cell activity in moderately en durance-trained and ethanol-consuming mice. Independent of ethanol exp osure, NK cell activity in nylon wool-nonadherent (NWNA) splenocytes i s lower in trained than in sedentary control mice (Blank et al. J. App l. Physiol. 72: 8-14, 1992). Reduced activity may result from a genera lized loss of cytolytically active cells, redistribution of NK cells f rom the spleen to other body compartments, or disruption of paracrine regulation of NK cells after removal of nylon wool-adherent cells. To examine these possibilities, NK cell cytolytic activity was determined in nonenriched splenocytes from treadmill-trained and ethanol-consumi ng mice. Lymphocyte subpopulations in nonenriched splenocytes and NWNA splenocytes were also compared. Peripheral blood lymphocyte subpopula tions were determined to examine combined effects of training and etha nol intake on regional distribution of lymphocytes in blood and spleen . NK cell activity in nonenriched splenocytes from trained water-drink ing mice was not reduced compared with that in sedentary mice; rather, cytolytic activity was moderately enhanced (17% increase in lytic uni ts, P < 0.05). Training did not change percentages of T-cells, B-cells , and NK [NK1.1(+) and large granular lymphocytes (LGL-1(+))] cells or the LGL/ NK ratio in the spleen and blood. NK cell cytolytic activity was significantly reduced in nonenriched splenocytes from ethanol-con suming mice, independent of training. These findings support the hypot hesis that moderate-intensity endurance training influences splenic NK cell function by modulating paracrine regulation of NK cells. In the case of combined chronic exercise and ethanol intake, training did not protect against ethanol-related decrease in percentage of NK1.1(+) ce lls or in its LGL-1 subset, indicating that loss of cytolytically acti ve cells contributes to decreased NK cytotoxicity in trained ethanol-c onsuming mice.