Effects of a selective neutral endopeptidase and a nonselective neutral endopeptidase/endothelin-converting enzyme inhibitor on lipopolysaccharide-induced endotoxaemia in anaesthetized Sprague-Dawley rats.

The gene expression and levels of endothelins (ETs) are increased in various animal models of lipopolysaccharide-(LPS) induced septic shock as well as in patients with endotoxaemia (ENDO). A positive correlation was reported between the expression and production of ETs, and the severity of haemodynamic and haematological disturbances, organ injury and circulatory failure in ENDO. Previous studies using ET(A)- and/or ET(B)-receptor antagonists exacerbated the effects of LPS in anaesthetized and conscious rats. We investigated the effect of a selective neutral endopeptidase (NEP) (CGS 24592) or a mixed NEP/endothelin-converting enzyme (ECE) (CGS 26303) inhibitor in LPS-induced ENDO in anaesthetized Sprague-Dawley rats. Four hours post-LPS injection, blood pressure was 39% lower in the presence of CGS 26303, compared to control-saline or LPS-injected rats. In rats treated with CGS 26303, white blood cells and platelet counts decreased, whereas lymphocytes increased. In addition, progressive liver dysfunction, characterized by increases in plasma bilirubin and alanine transferase, became even more apparent (higher than in those injected with LPS). Plasma creatinine and blood urea were similar to those of the LPS-injected group. Similar results were observed with CGS 24592. Thus, these inhibitors enhanced some, but not all, of the LPS-induced deleterious effects.