NATURAL-KILLER-CELL RESPONSE TO EXERCISE IN HUMANS - EFFECT OF HYPOXIA AND EPIDURAL-ANESTHESIA

For the response of immunologically competent blood cells to exercise, the importance of afferent nerve impulses was evaluated. On separate days, seven males cycled in a recumbent position approximate to 60% of maximal O-2 uptake with and without sensory nerve blockade by lumbar epidural anesthesia. Blood samples were collected after 60 min of rest , 20 min of exercise, and 120 min postexercise. Subsequently, on each day, the subjects were exposed to 11.5% O-2-88.5% N-2 for 10 min. This was followed by 20 min of hypoxic exercise at the same work rate, and a final blood sample was obtained. The concentrations of lymphocytes expressing the cluster designation (CD) cell-surface antigens CD3, CD4 , CD8, and CD14 became elevated during exercise, and these responses w ere enhanced by hypoxia (P less than or equal to 0.01). The most prono unced changes were within the concentrations of CD16+ and CD56+ natura l killer cells, which increased twofold during normoxic and fivefold d uring hypoxic exercise (P less than or equal to 0.01). Sensory nerve b lockade decreased the number of CD3+ and CD4+ cells and increased the percentage of CD16+ cells, independent of exercise and hypoxia (P less than or equal to 0.05). Sensory nerve blockade caused minor enhanceme nt in the increase of unstimulated natural killer cell activity during exercise (P = 0.07) and enhanced the interferon-cr-stimulated activit y at normoxia (P less than or equal to 0.05), whereas no effect was de tected at hypoxia. The results demonstrate that the responses of immun ological competent cells to normoxic and hypoxic exercise are not abol ished by blockade of nerve impulses from active muscle.