Although its role and importance is less well studied, carbon monoxide (CO) has been identifi ed as the second gasotransmitter in the GI tract. This study was performed to investigate the effect of modifying the endogenous CO production by altering heme oxygenase (HO) activity either by induction through hemin administration or inhibition by zinc mesoporphyrin administration on gastric secretion and ulceration induced by either cold restraint stress (CRS) or indomethacin (IND) treatment in

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... male albino rats. Our results revealed that hemin signifi cantly increased HO-1 levels with an increase in carboxyhemoglobin (COHb) level while zinc mesoporphyrin signifi cantly decreased HO-1 levels with a decrease in COHb level in all groups. Hemin pretreatment signifi cantly attenuated the gastric mucosal lesions induced by CRS and IND administration, which was accompanied by signifi cant reduction in free and total acidity of gastric secretion, decreased proteolytic activity and marked attenuation of lipid peroxidation inspite of decreased NO and PGE 2 levels. On the other hand, Inhibition of HO-1 activity by zinc mesoporphyrin prevented most of the effects caused by hemin administration except for its similar reduction in gastric mucosal NO and PGE 2 levels. On conclusion, Hemin exerts a protective effect against CRS and IND-induced gastric ulcers possibly via inducing HO-1 and increasing endogenous production of CO (Tab. 2, Fig. 4, Ref. 75). Text in PDF www.elis.sk.