SUPPRESSED PRODUCTION OF NITRIC-OXIDE AS A CAUSE OF IRREGULAR CONSTRICTION OF GASTRIC VENULES INDUCED BY THERMAL-INJURY IN RATS

Microcirculatory disturbance is a crucial step in development of gastr ic mucosal lesions. In this study we investigated the influence of nit ric oxide (NO) on the irregular constriction of gastric venules observ ed in rats subjected to thermal injury. Male Wistar rats were anesthet ized and a 30% full skin thickness dorsal burn was inflicted. Microvas cular images in the submucosal layer and basal region of the gastric m ucosa were obtained through an intravital microscope. Distribution of constitutive-type nitric oxide synthase (cNOS) was observed by the imm unofluorescence method. Venule walls were basically smooth In the cont rol group (no injury), whereas irregular constrictions tended to be ob served in the 5-h group (5 h after thermal injury). Venule diameter wa s significantly smaller in the 5-h group. Ln the control group, cNOS-a ssociated fluorescence was found on the venule endothelium, whereas it was almost negligible after thermal injury. A NO donor, 3-morpholinos ydnonimine hydrochloride, simultaneously diminished the thermal injury -associated venule constriction and irregularity of venule walls. Ther efore, the present study suggests that venule constriction. which is o bserved 5 h after thermal injury, is related to decreased NO productio n by endothelial cNOS and is a cause of irregularity of the venule wal ls.