PROTECTIVE MECHANISMS OF Oryza glaberrima VARIETIES ON INDOMETHACIN-INDUCED GASTRIC ULCERATION IN MALE WISTAR RATS

Abstract

Consumption of Oryza glaberrima (Nigerian brown rice) varieties has increased over the years due to its good nutritional values. Unlike polished rice which lacks bran and has been documented to possess ulcerogenic activities, Oryza glaberrima species have their bran retained. Rice bran has been reported to possess anti-ulcerogenic properties. This study was designed to investigate the anti-ulcer mechanisms of two Oryza glaberrima varieties (locally called Alasoosun and Tapa) on indomethacin-induced gastric ulcer in male Wistar rats. Alasoosun and Tapa varieties obtained from Oke-Imesi (Ekiti State) and Patigi (Kwara State), respectively were authenticated at the Department of Botany, University of Ibadan with voucher number UIH-22662. Proximate and photochemical analyses were performed according to standard procedures. Rice varieties were ground and mixed with 20% standard rat feed and all feeding was given ad libitum for eight weeks. This study was divided into three phases. With each phase consisting of twenty-five rats (150-170g), randomly distributed into five groups (n=5) as follows; normal control (standard rat feed), ulcerated control (standard rat feed), Alasoosun (80%), Tapa (80%), rice bran (80%). At the end of the eighth week of treatment, gastric ulcer was induced after overnight fasting in all groups using indomethacin (40 mg/kg p.o.) except the ulcerated control group. Gastric ulcer score and index were determined using standard procedures by plannimetry four hours after indomethacin administration. Gastric mucosal blood flow was measured with Laser-Doppler flow meter. Gastric adherent mucus content, protein level, Malondialdehyde (MDA), suflhydryl, Nitric Oxide (NO) and activities of Superoxide Dismutase (SOD) were measured using a spectrophotometer. Prostaglandin E2 (PGE2) was assessed using ELISA. Histological evaluation of haematoxylin and eosin stained gastric tissue was done using light microscopy. Data were analysed using ANOVA at α0.05. Proximate analysis revealed highest percentage of fiber in rice bran (38.47%) compared to Alasoosun (1.67%) and Tapa rice (1.96%). Phytochemical analysis revealed the presence of higher quantities of alkaloids, tannins, saponins, phenolic compounds and cardiac glycosides in rice bran relative to Alasoosun and Tapa rice. Gastric ulcer was significantly reduced in Alasoosun (2.00 ± 0.29), Tapa (3.83 ± 0.17) and rice bran pre-treatment groups (1.25 ± 0.72) compared to ulcerated control (7.58 ± 0.71). The MDA level (nmol/mg protein) was significantly decreased in control (0.79 ± 0.06), Alasoosun (0.52 ± 0.04),Tapa (0.77 ± 0.03) and rice bran (0.51 ± 0.12) compared to ulcerated control (1.73 ± 0.03). Significant decrease in gastric mucosal blood flow, adherent mucus content, SOD, sulfhydryl, NO and PGE2 level observed in ulcerated control were ameliorated in Alasoosun, Tapa and rice bran. Histological evaluation showed increased neutrophil infiltration with focal necrosis in ulcerated control which was absent in the other groups. Alasoosun rice, Tapa rice and rice bran pre-treatment may exert gastroprotective activities via increased vasodilatation, gastric mucosal blood flow, gastric mucus content, prostagladin E2 level and anti-oxidative activities.