Epinephrine causes a reduction in lymph node cell output in sheep

The lymphatic system has a critical role in the return of fluids, proteins, and cells to the circulatory system. However, the effects of stress, inclu ding exercise, on this system have not been adequately studied. We investig ated the effect of a physiological dose (1 mg) of epinephrine (Epi) on lymp h flow, cell concentration, and lymphocyte subsets in efferent subcutaneous lymph in sheep. Blood leukocyte numbers, differential, lymphocyte subsets, and blood and lymph pools of lymphocytes were determined simultaneously. A significant acute increase in lymph flow was followed by a post-injection decrease in flow and cellular output. No changes in lymphocyte subsets or p ools of lymphocytes were seen in either blood or lymph. The timing of eleva ted plasma and lymph concentrations of Epi and norepinephrine (NE) correspo nded with the increased lymph flow. In conclusion, Epi injection caused no change in lymphocyte subset distribution, leukocyte concentration, or pools of lymphocytes. A decrease in lymph flow and cellularity was documented po st-injection, indicating that lymphatic tissue has no role in the leukocyto sis seen after Epi injection. Lymphocyte retention by lymph nodes, however, may contribute to post-injection lymphopenia.