RESUMO
Baccharis illinita DC (Compositae) is used in folk medicine to treat gastric disturbances. Preliminary studies with other extracts of B. Illinita showed gastric protection against ethanol-, indometacin- and stress-induced ulcers and the inhibition of gastric secretion. Based on these data, the aim of this study was to verify the pathways involved in the inhibition of gastric secretion. The chloroform extract (CE) of flowers from B. illinita (3, 10, 30 and 100 mg kg(-1) i.p.) tested on rats with pylorus ligature reduced the volume and the total acidity of gastric content by approximately 50% (ED50 = 69 mg kg(-1)). Treatment with CE (100 mg kg(-1) i.p.) reduced the gastric total acidity stimulated by histamine, bethanechol and pentagastrin to 42%, 27% and 57% of that in the stimulated control group, respectively. The CE (10, 30 and 100 microM) inhibited H+/K+ ATPase activity in-vitro, with an IC50 of 37 microM. The isolated flavonoid luteolin (1, 3, 10 and 30 microM) also inhibited H+/K+ ATPase activity by 50%, at a dose of 30 microM. Our results suggest that the reduction in gastric secretion occurs through inhibition of H+/K+ ATPase, which is the final step in acid secretion and therefore one of the most important steps.