[Role of intestinal lymphatic in myocardial injury in rats receiving hemorrhage and lipopolysaccharide challenge].

Objective: To explore the effect of mesenteric lymph duct ligation in protecting myocardial injury in rats after hemorrhage and lipopolysaccharide (LPS) challenge.

Methods: Wistar rats were randomly divided into the sham group, non-ligation group and ligation group, and the "two-hit" injury model was reproduced by hemorrhage and LPS administration. Mesenteric lymph was blocked by ligating mesenteric lymph duct in ligation group after hemorrhage. After 24 hours of the assault, myocardial tissue was harvested and homogenized. The activity of myeloperoxidase (MPO) and ATPase and the contents of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) were determined in myocardial homogenate. At the same time, myocardium was pathologically studied. Apoptosis cell rate of myocardium was determined by method of terminal-deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL), the expression of bcl-2 and bax protein was determined by immunohistochemical method.

Results: After hemorrhage and LPS challenge, the level of MPO [(0.23+/-0.08) U/g], TNF-alpha [(9.99+/-2.74) microg/g] and IL-6 [(31.57+/-12.71) microg/g] in myocardial homogenate of non-ligation group were significantly higher than those of sham group [MPO: (0.12+/-0.03) U/g, TNF-alpha: (4.17+/-1.35) microg/g, IL-6: (17.86+/-5.17) microg/g, respectively, all P<0.01], and the activity of ATPase was significantly lower. MPO [(0.13+/-0.03) U/g], TNF-alpha [(5.57+/-1.65) microg/g] and IL-6 [(23.24+/-5.95) microg/g] in myocardial homogenate of ligation group were significantly lower (P<0.05 or P<0.01), and the ATPase activity was significantly higher compared with non-ligation group. The apoptosis rate [(22.7+/-6.9)%] and expression of bax protein (104.5+/-11.4) of myocardial cells in non-ligation group were significantly higher compared with sham group [apoptosis rate: (3.8+/-1.2)%, bax protein: 142.1+/-10.9] and ligation group [apoptosis rate: (8.4+/-2.8)%, bax protein: 128.4+/-9.6], and expression of bcl-2 protein of non-ligation group (196.4+/-19.3) was significantly lower than that of sham group (132.2+/-12.3) and ligation group (165.1+/-11.6, all P<0.01).

Conclusion: The results demonstrate that the mesenteric lymph duct ligation ameliorate the myocardial injury in rats subjected to hemorrhage and LPS by reducing the inflammatory mediators of TNF-alpha and IL-6 levels, upregulating the bcl-2 protein expression and improving membrane ATPase activity of myocardium.