N-acetylcysteine does not affect the lymphocyte proliferation and natural killer cell activity responses to exercise.

This study evaluated whether N-acetylcysteine (NAC) attenuates the reduced lymphocyte proliferation and natural killer (NK) cell activity responses to exercise in humans. Fourteen oarsmen were double-blind randomized to either NAC (6 g daily for 3 days) or placebo groups. During 6-min "all-out" ergometer rowing, the concentration of lymphocytes in the peripheral blood increased, with no significant difference between NAC and placebo as reflected in lymphocyte subsets: CD4(+), CD8(+), CD16(+), and CD19(+) cells. The phytohemagglutinin-stimulated lymphocyte proliferation decreased from 9,112 +/- 2,865 to 5,851 +/- 1,588 cpm (P < 0.05), but it was not affected by NAC. During exercise, the NK cell activity was elevated from 17 +/- 3 to 38 +/- 4% and it decreased to 7 +/- 1% below the resting value 2 h into recovery. Yet, when evaluated as lytic units per CD16(+) cell, the NK cell activity decreased during and after exercise without a significant effect of NAC. We conclude that NAC does not attenuate the reduction in lymphocyte proliferation and NK cell activity associated with intense exercise.