Changes in substance P in the jejuna of rats after burns

Radioimmunoassay (RIA) was used to determine the dynamic changes of immunoreactive substance P (iSP) in the jejuna of rats (TBSA 30 per cent full skin thickness burn) during the first 72 h postburn. Immunohistochemistry and image analysis techniques were used to observe and quantitate the SP immunoreactivity (SP-IR) of positive nerve fibres in the villi of jejuna postburn. Changes in the amount of iSP in jejuna of burned rats were: (1) iSP increased significantly at 1 h postburn, and the high level of iSP lasted 4 h; it then decreased greatly 8 h later with the low level of iSP persisting for 72 h. (2) Significant changes in SP-IR-positive nerve fibres in the villi after burn were shown by the immunohistochemical studies including the morphoses; the distributive densities and SP-IR-positive products in the SP-IR-positive nerve fibres. The results quantified by image analysis showed similar alterations in the distributive densities and SP-IR-positive products in the nerve fibres in the villi during 72 h postburn; which were distinctly elevated by 1 hr then dropped by 8 h and 12 h and finally elevated again. The results indicated that the irritation-release and consumption of SP occurred in jejuna of rats after burns. It might be that SP contributed to the postburn intestinal lesion in rats by bioactivities, such as enhancing the vascular permeability and regulating the intestinal movement. The SP peptidergic nerve fibres of the villus had a direct effect on the damage to mucosal epithelia.