Role of reduced glutathione and nitric oxide in the black tea extract-mediated protection against ulcerogen-induced changes in motility and gastric emptying in rats.

The aim of the present study was to investigate the underlying mechanism of the role of hot water extract of black tea [Camellia sinensis (L). O. Kuntze Theaceae] in normalizing the changes in intestinal transit and gastric emptying induced by various ulcerogenic agents in experimental rats. Intestinal transit as well as gastric emptying were significantly reduced in rats treated with glutathione (GSH) depleting agents, diethyl maleate (DEM), indoacetamide (IDA) and N-ethyl maleimide (NEM). Prior oral administration of black tea extract (BTE) at 20 ml/kg of a 10% solution, i.g. once a day for 7 days significantly increased the intestinal transit and gastric emptying with restoration of serum GSH level. Singular administration of succimer (60 mg/kg, i.g.), the standard sulfhydryl containing antiulcer agent used as a reference drug, was also effective. Increase in intestinal transit caused by BTE was reversed both by N-omega-nitro-L-arginine methyl ester (L-NAME) (25 mg/kg, i.p.) and N-omega-monomethyl-L-arginine (L-NMMA) (25 mg/kg, i.p.), but not with N-omega-nitro-D-arginine methyl ester (D-NAME) (25 mg/kg, i.p.). Furthermore, restoration of intestinal nitric oxide synthase (NOS) activity was found to be associated with BTE treatment. These results provide evidence that nitric oxide may play a role in BTE-mediated improvement of intestinal motility changes and gastric emptying induced by DEM, IDA and NEM.