Comparative study of nitric oxide production induced by selective estrogen receptors alpha and beta agonists in rats

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Graciliano Ramos Alencar do Nascimento
Célia Akemi Kanashiro
Michelle Serock
Raouf Khalil
Maria Aparecida da Silva Pinhal

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BACKGROUND AND OBJECTIVES: Nitric oxide (NO) is a potent vasodilator and estrogen-mediated vasodilation that increases NO production. The association of the vascular endothelium, gender and vasodilation induced by estrogen is due to the activation of two estrogen receptors, alpha (ERa) and beta (ERb). The aim of this study was to compare NO production stimulating receptors ERa and ERb with the use of selective agonists in thoracic aortas of rats. METHODS: Aortic rings were either treated with 17 β-estradiol (17-BE2); acetylcholine (Ach); 4,4’,4-[4-propil-(1H)-pirazol-1,3,5-triyl]tris-phenol (PPT), and 2,3-Bis(4-hydroxyphenyl)-propionitrile (DPN), or left untreated, and the concentration of NO was determined by spectrophotometry method. RESULTS: The females presented a higher basal concentration of nitrite than males. PPT determined increased production of nitrite in both females and males, compared to 17-beta-estradiol (17-BE2). In males, the production of nitrite induced by DPN and PPT was higher than that induced by 17- BE2. The stimulation with 17-BE2 increased the production of nitrite in females compared to males. Regardless the gender, the stimulation of aortic rings by PPT caused a greater production of nitrite compared to that induced by 17-BE2. Interestingly, the stimulation of aortic rings from males with DPN provided an increase in the nitrite production compared to the levels induced by 17-BE2 incubation. CONCLUSION: The stimulation of estrogen receptor (ER) by PPT provides greater production of nitrite than 17-BE2 regardless of gender; in males, the stimulation of ER by DPN provides bigger production of nitrite than 17-BE2; the basal production of nitrite is higher in females compared to males.

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