Treadmill exercise training blunts suppression of splenic natural killer cell cytolysis after footshock

This study extended to treadmill exercise training our prior report (Dishma n RK, Warren JM, Youngstedt SD, Yoo H, Bunnell BN, Mougey EH, MeyerhoffJl, Jaso-Friedmann L, and Evans DL. JAppl Physiol 78: 1547-1554, 1995) that act ivity wheel running abolished the suppression of footshock-induced natural killer (NK) cell cytolysis. Twenty-four male Fischer 344 rats were assigned to one of three groups (n = 8, all groups): 1) a home-cage control group, 2) a sedentary treatment group, or 3) a treadmill-running group (0 degrees incline, 25 m/min, 35 min/day, 6 days/wk). After 6 wk, the treadmill and se dentary groups received 2 days of footshock. Splenic NK cytotoxicity was de termined by standard 4-h Cr-51 release assay. Percentages of lymphocytes we re determined by flow cytometry. Plasma levels of ACTH, corticosterone, and prolactin concentration were measured by radioimmunoassay. After footshock , percentage of lysis relative to home-cage controls was 40% and 80% for se dentary and treadmill-trained animals, respectively (P < 0.05). Our results indicate that the protective effect of chronic exercise on innate cellular immunity in the Fischer 344 male rat is not restricted to activity wheel r unning, nor is it explained by elevations in basal NK activity, increased p ercentages of splenic NK and cytotoxic T cells, or increased plasma levels of ACTH, corticosterone, and prolactin.