Olfactory receptor. The activity of this receptor is probably mediated by G-proteins wich induce elevation of intracellular Ca(2+), cAMP and activation of phosphorylation of the protein kinases PKA and MAPK3/MAPK1. Activation of OR51E2 may affect melanocyte proliferation, differentiation, and melanogenesis and may increase proliferation and migration of primary retinal pigment epithelial (RPE) cells (By similarity). Activated by the short chain fatty acids (SCFA), acetate and propionate (PubMed:23401498). In response to SCFA, may positively regulate renin secretion and increase blood pressure (PubMed:23401498). May also be activated by steroid hormones and regulate cell proliferation (By similarity). Activated by L-lactate in glomus cells (PubMed:26560302, PubMed:30258151). In brain, expressed in medulla oblongata by cells close to the fourth ventricle, in the area postrema, the nucleus tractus solitarius (PubMed:11707321). Expressed in olfactory epithelium and vomeronasal organ (PubMed:11069588). Expressed in kidney by large renal vessels, renal afferent arterioles, and extrarenal vascular beds. In small resistance vessels the expression is restricted to cells of the juxtaglomerular afferent arteriole, which mediate renin secretion. Also detected in small blood vessels in a variety of tissues including heart, diaphragm, skeletal muscle, and skin. In the heart, esophagus, and stomach it is detected in axons of autonomic neurons and neurons of the enteric plexus (PubMed:23401498). Also detected in colon and liver (PubMed:23401498). Expressed in the glomus cells of the carotid body (PubMed:26560302). Primarily detected between 11 dpc and 12 dpc. Expressed at 12 dpc in the dorsal region of the developing nasal cavity and in the mesenchyme located between the olfactory epithelium and the presumptive olfactory bulb. In the medulla oblongata, first detected at 17 dpc. In the area postrema and the nucleus tractus solitarius expression peaks at P20 and then decreases slightly. Knockout mice display reduced baseline blood pressure. Belongs to the G-protein coupled receptor 1 family. Contradictory results have been reported for activation by beta-ionone in human and mouse. Beta-ionone does not activate OR51E2 in mouse. This difference may depend on the different methods used for these experiments, or may be due to species difference. Conflicting results for the role of OR51E2 in the regulation of breathing and its role as a hypoxia sensor activated by lactate are reported (PubMed:26560302, PubMed:30258151). It was first described as a hypoxia sensor in the breathing circuit by sensing lactate produced when oxygen levels decline (PubMed:26560302). A recent study fails to confirm a role for OR52E2 in this pathway (PubMed:30258151). Conflicting results may reflect the use of different strain backgrounds (PubMed:30258152, PubMed:26560302, PubMed:30258151).