Androstenone is the first mammalian steroidal pheromone to be identified. Pheromones are chemicals that animals use to communicate within a species. Pheromone detections are related to vomeronasal organ (VNO) and olfactory epithelium (OE) in mammals. Olfactory Receptor Family 7 Subfamily D Member 4 (OR7D4) is an odorant receptor that responds to androstenone. Several studies indicated that spray with androstenone changes behaviors of the boar and dogs. However, the expression of OR7D4 in VNO and OE was not reported in mammals except human. Thus, the main objectives of this study were to investigate the expression of OR7D4 in VNO and OE of horses. Tissue samples were collected from the VNO and nasal cavity of 6 thoroughbred horses. The presence of OR7D4 gene was investigated with reverse transcription–polymerase chain reaction. The expression of OR7D4 was determined using Western blot and immunofluorescence. As a result, the bands for OR7D4 were observed at approximately 462 bp. The protein band of OR7D4 of VNO and OE was detected at 38 kDa. Immunofluorescence result showed that the cilia and cytoplasm of olfactory receptor cells of VNO and nasal cavity tissues were immunolabeled with OR7D4 antibody. The intensity of OR7D4 protein bands in the ventral region of the ethmoidal concha tissues was not significantly different between mares and geldings. In conclusion, thoroughbred horses are capable of androstenone perception through OR7D4 expressed in the VNO and OE.

雄烯酮是第一个被鉴定的哺乳动物甾体信息素。信息素是动物用来在物种内进行交流的化学物质。信息素检测与哺乳动物的犁鼻器官 (VNO) 和嗅觉上皮 (OE) 有关。嗅觉受体家族 7 亚家族 D 成员 4 (OR7D4) 是一种对雄烯酮有反应的气味受体。几项研究表明，喷洒雄烯酮会改变公猪和狗的行为。然而，OR7D4 在 VNO 和 OE 中的表达在除人类之外的哺乳动物中未见报道。因此，本研究的主要目的是研究 OR7D4 在马的 VNO 和 OE 中的表达。从 6 匹纯种马的 VNO 和鼻腔收集组织样本。OR7D4的存在用逆转录-聚合酶链反应研究基因。使用蛋白质印迹和免疫荧光测定 OR7D4 的表达。结果，在大约 462 bp 处观察到 OR7D4 的条带。在38 kDa处检测到VNO和OE的OR7D4蛋白条带。免疫荧光结果显示，VNO和鼻腔组织嗅觉受体细胞的纤毛和细胞质被OR7D4抗体免疫标记。OR7D4蛋白条带在筛骨组织腹侧区域的强度在母马和骟马之间没有显着差异。总之，纯种马能够通过 VNO 和 OE 中表达的 OR7D4 感知雄烯酮。