[An experimental study on the relationship between early myocardial injury and the in situ expression of TNFalpha mRNA in burned rats with endotoxemia].

Objective: To observe the in situ expression of TNF mRNA and protein in myocardial cell, so as to explore the possible mechanism of early myocardial injury in scalded rats with endotoxemia.
Methods: One hundred and seventy eight Wistar rats inflicted with 20% TBSA III degree napalm burn compound with endotoxemia and multiple organ injury were employed as the model and were randomly divided into four groups as follow. (1) burn and infusion group (BI): the rats were burned and infused with endotoxin. (2) simple burn group (S): the rats were burned only. (3) simple endotoxin infusion group (EI): the rats were only infused with endotoxin. (4) normal control (C). The observation time points were designed to be 0.5, 1, 3, 6, 12, 24 and 48 postburn hours (PBH). The morphological and functional changes in rat myocardium, the change in serum TNFalpha, the cellular location and distribution of TNFalpha mRNA and proteins were observed by light microscope (LM), electronic microscope (EM), ELISA, immunohistochemistry and in situ hybridization staining.
Results: There exhibited a series of pathomorphological changes in the myocardium at early postburn stage in rats of BI group, such as wavy degeneration of myocardial fibers, the formation of contractile bands, fragmentation of myocardial fibers and focal cytoplasmic lysis, etc. The left ventricular systolic pressure (LVSP) and the maximum change rate of intraventricular pressure (plus minus dp/dtmax) decreased significantly (P < 0.01). Serum TNFalpha level increased obviously at 1 PBH (P < 0.01) and peaked at 3 similar 6 PBH. It was found that TNFalpha mRNA was principally located in myocardial cells and in a part of inflammatory cells. But these milder pathomorphological changes in myocardial injury were found in rats of S and EI groups. In addition, there appeared elapsed TNFalpha peak values and relative weaker expression of myocardial TNFalpha mRNA.
Conclusion: TNFalpha mRNA and protein could be expressed in myocardium in burned rats with endotoxemia which might be one of the origins of TNF in participating in the development of early postburn myocardial structural and functional injury.