Tumour necrosis factor-alpha, but not septic plasma depresses cardiac myofilament contraction

In sepsis, myocardial depression may be caused by mediators released as part of the inflammatory reaction, lumour necrosis factor alpha (TNF alpha) is one mediator that may contribute to this depression. In the present study, we contrasted the effects of TNF alpha and septic plasma fraction (SP) obtained from an E. coli model on contractile tension in intact and skinned canine ventricular trabecular (VT) preparations. The objectives were to determine whether SP or TNF alpha could impair contractile tension at the level of the myofilaments, and to determine the extent to which TNF alpha may account for myocardial depression found in E. coli sepsis.

Measurements of isometric tensions were made after TNF alpha and SP (10,000 to 30,000 MW fraction) were added to respective intact or skinned canine VT preparations. In the skinned preparation, trabeculae were chemically skinned with Triton X-100.

Septic plasma caused a decrease in contraction in the intact preparation compared with preseptic plasma (50 +/- 7 vs 33 +/- 7%, P < 0.05), but had no effect in the skinned preparation. On the other hand, TNF alpha (30 ng.ml-1) caused an approximately 50% reduction in tension (29 +/- 2 mg vs 16 +/- 5 mg) in the skinned preparation (P < 0.05), but had no effect in the intact preparation.

These results suggest that TNF alpha and SP act through different mechanisms. While SP requires an intact membrane, TNF alpha impairs function by a direct effect on the myofilaments.