ROLE OF ENDOGENOUS AND EXOGENOUS NITRIC-OXIDE ON INTESTINAL-MUCOSA AND MICROFLORA IN THE RAT

In the present study the effects of exogenous and endogenous nitric ox ide (NO) on intestinal bacteria and on the intestinal tissue integrity have been investigated in healthy rats and in rats receiving bacteria l endotoxin (LPS). A segment of jejunum was taken in order to evaluate tissue damage and hematoxylin-eosin staining; microbiological studies were carried out collecting stool samples. Administration of LPS (5 m g kg(-1) i.v.) induced a moderate jejunal damage, which was completely prevented by N-G-nitro-L-arginine methyl ester (L-NAME, 5 mg kg(-1) s .c.), thus suggesting a damage of endogenous NO on the intestinal muco sa; sodium nitroprusside (SNP, 10 mg kg(-1) os) reduced significantly jejunal damage induced by LPS. Endogenous NO produced by the administr ation of LPS resulted to be cytotoxic for all examined aerobic and ana erobic bacteria, while exogenous NO, released from SNP, showed an inhi bitory effect only on Entero. faecalis and E coli growth. From our dat a, it seems reasonable to conclude that high local levels of NO are re quired in order to observe jejunal damage and cytotoxic effects on aer obic and anaerobic faecal flora.