Mesenteric lymph duct ligation provides long term protection against hemorrhagic shock-induced lung injury

Recently we have shown that ligation of the main mesenteric lymph (MLN) duct prior to an episode of hemorrhagic shock (HS) prevents shock-induced lung injury. Yet, ligation or diversion of intestinal lymph immediately prior to injury is not clinically feasible. Diversion of intestinally derived lymph after injury to protect against secondary insults is possible, but it is not known how long the protective effects of lymph ligation would last. Thus, we tested whether ligation of the MLN duct seven days prior to HS would still be protective. Male Sprague-Dawley rats were subjected to laparotomy with or without MLN duct ligation. Seven days later, half of the sham and actual MLN duct ligated animals randomly were selected to undergo HS (30 mmHG for 90 min). The other half of the animals was subjected to sham shock. Lung permeability, pulmonary myeloperoxidase (MPO) activity, and bronchoalveolar fluid (BALF) protein content were used to determine lung injury. Lymphatic division 7 days prior to HS continued to prevent shock induced lung injury as assessed by a lower Evans Blue dye concentration, BALF protein and MPO activity. In addition, there was no evidence of Patent Blue dye in the previously ligated MLN duct. Since ligation of the main mesenteric lymphatic duct continues to protect against shock-induced lung injury 1 week after duct ligation, it is feasible that lymphatic ligation performed after an injury remains protective against certain secondary insults for at least 1 week.