S. PrachayasittikulO. WongsawatkulA. WorachartcheewanS. RuchirawatV. PrachayasittikulSrinakharinwirot UniversityMahidol UniversityChulabhorn Research Institute2018-09-242018-09-242010-08-20International Journal of Pharmacology. Vol.6, No.4 (2010), 375-38018125700181177752-s2.0-77955644960https://repository.li.mahidol.ac.th/handle/20.500.14594/29918The aim of study is to investigate effects of orotic acid (OA) on phenylephrine-induced contraction of rat thoracic aorta and its antioxidative activity. Results showed that the OA exhibited maximal vasorelaxation in dose-dependent manner with ED50 of 3.1?×10-7 M, but the effect was less than those of acetylcholine (ACh)-induced nitric oxide (NO) vasorelaxation. Significant reductions of the vasorelaxations were found in the presence of either NG-nitro-L-arginine methyl ester (L-NAME) or indomethacin (INDO). Synergistic effects were observed in the presence of L-NAME plus INDO that led to loss of vasorelaxation of both the ACh and the OA. In addition, complete loss of the vasorelaxation was manifested under removal of endothelial cells. This implies that the vasorelaxations are mediated by partially endothelium-induced NO and prostacyclin. The OA exhibited antioxidative activity in both DPPH and SOD assays. The significant results reveal novel actions of the OA as vasorelaxants and superoxide scavenger which are benefits as therapeutic uses and health supplements. © 2010 Asian Network for Scientific Information.Mahidol UniversityPharmacology, Toxicology and PharmaceuticsArticleSCOPUS