Effect of antioxidants on pyrogallol-induced delay in gastric emptying in rats.

The effect of a free radical generator pyrogallol on gastric emptying was studied in rats. Pyrogallol at doses of 25, 50, 100 and 150 mg/kg (i.p.) produced dose-dependent inhibition of gastric emptying. Pretreatment with vitamin C (100 and 500 mg/kg, p.o.), and vitamin E (100 and 500 mg/kg, p.o.) significantly reversed the inhibition in gastric emptying caused by pyrogallol 100 mg/kg. However, the combination of vitamin C and vitamin E (100 mg/kg) produced synergistic effect. Glutathione (100 mg/kg i.v.) 5-min pretreatment also reversed the inhibition of gastric emptying caused by pyrogallol 100 mg/kg. Ondansetron (3 mg/kg, p.o.) significantly reversed the pyrogallol effect. The effect of pyrogallol on malondialdehyde (MDA) levels and 5-HT levels in the stomach tissue was also studied. Pyrogallol at a dose of 100 mg/kg, i.p., significantly increased MDA levels and 5-HT levels in the stomach. Pretreatment with a combination of vitamin C and vitamin E (100 mg/kg, p.o.) and glutathione (100 mg/kg, i.v.) significantly ameliorated the rise in stomach tissue MDA caused by pyrogallol but had no significant effect on the rise in 5-HT levels caused by pyrogallol. The effect of different doses of 5-HT on gastric emptying was also studied. 5-HT had a differential effect on gastric emptying. The low and high doses (0.1, 0.3 and 30 mg/kg, i.p.) significantly inhibited the gastric emptying while doses ranging from 1 to 10 mg/kg, i.p., had no significant effect on the gastric emptying. The pretreatment with antioxidants, combination of vitamin C and vitamin E (100 mg/kg each, p.o.) and glutathione (100 mg/kg, i. v.) had no effect on the 5-HT (0.3 mg/kg, i.p.)-induced delay in gastric emptying. The result indicate the role of free radicals gastric emptying, and antioxidants may be of potential therapeutic value in disease conditions where free radicals are known to be released and the gastrointestinal effects are observed as symptoms or side effects of drug therapy.