Effects of f-Met-Leu-Phe-induced inflammation on intestinal lymph flow and lymphatic pump behavior

Previous studies in the literature indicate that intraenteric placement of the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (f-Met-Leu-Phe) evokes an intestinal inflammatory response characterized by an accumulation of interstitial fluid and increased lymph flow. Furthermore, it is known that movement of lymph away from the intestine is dependent on the rhythmic pumping of lymph by collecting lymphatics in the mesentery. The purpose of the present study was to determine whether the f-Met-Leu-Phe-induced increase in lymph formation is countered by an increase in lymphatic pump efficiency. Male Sprague-Dawley rats were anesthetized, and a segment of ileum with adjacent mesentery was exteriorized. The mesentery was positioned over an optical window, and a 100-microns collecting lymphatic was selected for study. The preparation was transferred to a video microscope, and the activity of the lymphatic pump was monitored under control conditions and during intraluminal infusion of 1 microM f-Met-Leu-Phe. Lymph propulsion by the lymphatic pump was calculated from the product of stroke volume and contraction frequency. In one group of animals, total lymph flow was determined by cannulating the lymphatic draining the ileal segment. Total lymph flow increased following f-Met-Leu-Phe placement in the intestine. The increased lymph flow was paralleled by a rise in lymphatic pumping. The rise in lymph propulsion by the lymphatic pump resulted exclusively from an increased stroke volume, inasmuch as contraction frequency did not change. The results of the present study suggest that activation of the lymphatic pump during acute inflammation may be important in preventing interstitial edema.