Abstract Body: Introduction: It is well known that lipid mediators secreted by brown adipose tissue (BAT) during cold exposure or beta-adrenergic stimulation can exert beneficial effects on glucose and lipoprotein homeostasis. Recently, Leiria et al. demonstrated that one of these mediators, 12-hydroxyeicosapentaenoic acid (12-HEPE), secreted by BAT, enhances glucose tolerance and insulin sensitivity through the stimulation of a G protein-coupled receptor (GPCR). However, the receptor that 12(S)-HEPE binds to exert its functions was unknown. Therefore, this study aimed to identify the GPCR that 12-HEPE binds to and to investigate whether 12-HEPE affects vascular reactivity. Methods: Screening of 70 non-olfactory GPCR candidates was conducted in HEK293 cells, either stimulated or not with 12-HEPE (5µM). Receptor activation was measured using the dynamic mass redistribution (DRM) assay. After identifying the potential receptor, we validated the result by monitoring intracellular Ca2+ levels through a dose-response curve for 12-HEPE. To study the biological effects resulting from this ligand-receptor interaction, thoracic aortic artery rings were isolated from 12-week-old C57BL6 male mice, and their contractile responses were monitored using a myograph in response to cumulative doses ranging from 100pM to 10µM of 12-HEPE. Results: Through DRM screening, we found that the thromboxane receptor (TP) exhibited the strongest interaction with 12(S)-HEPE (5µM). To validate the screening, we incubated HEK293 cells with 12-HEPE or U46619 and quantified intracellular calcium mobilization. Our data demonstrate that 12-HEPE is a partial TP agonist, with an EC50 of 314nM compared to 7.2nM for U46619. Furthermore, incubation of the thoracic aorta with 12-HEPE produced dose-dependent increases in arterial constriction (pEC50: 6.129 ± 0.174; Emax: 95.39 ± 15.72), and this effect was completely prevented by the thromboxane antagonist, TPA (1µM). Conclusions: Our results suggest that 12-HEPE is an endogenous partial agonist of the TP receptor, and such interaction is necessary for the biological effects of these lipids. Importantly, the vasoconstrictor effect mediated by 12-HEPE may be an important physiological adaptation to prevent body heat loss upon cold exposure, thus allowing for adequate temperature maintenance.