目的 对牦牛、迁饲黄牛及低海拔黄牛颈动脉体（CB）形态及CB中低氧相关因子的表达进行比较，探讨高原土生或迁饲动物CB适应慢性低氧的模式。 方法 采集青海地区海拔3000～4000m的9头牦牛、2500m的9头高山迁饲黄牛及甘肃平原海拔1300米的12头低海拔黄牛的CB，固定、切片、染色后行光学显微镜和电子显微镜比较观察，并对CB中低氧诱导因子-1α(HIF-1α)、一氧化氮合酶（NOS）、瘦素受体（LEPR）、促红细胞生成素（EPO）等低氧相关因子的表达进行免疫组织化学观察。 结果 相比黄牛，牦牛CB体积较小，不同海拔牦牛的CB大小、形态及主细胞数量差异无显著性，而迁饲黄牛CB体积较低海拔黄牛大。牦牛CB主细胞中明细胞、暗细胞和固缩细胞的数量百分比比例为67.1%∶28.2%∶4.7%,迁饲黄牛为78.5%∶18.6%∶2.9%，低海拔黄牛为87.3%∶10.2%∶2.5%；与低海拔黄牛相似，牦牛CB少部分明细胞胞质透亮，暗细胞胞核染色质较致密并呈粗颗粒状，而迁饲黄牛CB大部分明细胞胞质透亮，暗细胞胞核染色质致密，颗粒稀少。3种牛支持细胞形态差异无显著性。与低海拔黄牛相比，迁饲黄牛CB主细胞的少数核异染色质增多，个别形态异常，胞质内多数细胞器肿胀溶解，残留少量细胞器和致密核心囊泡。3种牛CB中均有不同程度的HIF-1a、NOS、LEPR、EPO的蛋白表达，其中牦牛CB中EPO蛋白表达阳性率较低海拔黄牛明显降低（P<0.05）。结论 海拔高度不是影响牦牛颈动脉体大小和主细胞数量的主要因素。迁饲黄牛CB主细胞中细胞类型的比例与牦牛有趋同性改变，但缺氧时行使功能的I型细胞功能系统受损，尚处于低氧环境下的习服阶段。慢性低氧可能主要影响牦牛和迁饲黄牛CB中EPO蛋白表达。

Objective Yak (Bos grunniens) is an indigenous mountain species and genetically adapted to high altitude. When cattle from low altitude is taken to a high altitude, it may develop hypoxic pulmonary artery hypertension known as brisket disease. We compared the morphological and histological variations of carotid body (CB) among yaks, migrated cattle and low altitude cattle. The results could provide important insights of the process of adaptive evolution. Methods The CBs were sampled from 9 indigenous yaks born and lived at 3000-4000 m, and 9 cattle whose ancestors migrated to high altitude at 2500m for several generations in Qinghai-Tibet plateau. In addition, 12 CBs of low altitude cattle living at 1300 m in Gansu were used as control. The samples were fixed, sectioned, stained, observed under an optical and an electron microscope. The expression of hypoxia-inducible factor-1α (HIF-1α), nitric oxide synthase (NOS), leptin receptor (LEPR) and erythropoietin (EPO) were observed by immunohistochemical methods. Results No significant difference was observed for the size of CB in yaks which lived in various altitude. Furthermore, the size, shape, and the percentage of chief cells and sustentacular cells from each CB of yaks had no significant difference either. However, the CB size of migrated cattle was the largest comparing to the lowland cattle and yaks. The CB of yaks was the smallest at size. The percentages of light chief cells, dark cells, pyknotic cells of each CB in yak were 67.1%∶28.2%∶4.7%, and that in migrated cattle were 78.5%∶18.6%∶2.9%, while that in lowland cattle were 87.3%∶10.2%∶2.5%. Similar to CB of lowland cattle, a small amount of clear cells of yak were of clear cytoplasm; and nuclear chromatin of dark cells was denser with more particles. In the CB in migrated cattle, the clear cells were mostly of clear cytoplasm, and few particles were investigated in nuclear chromatin of dark cells, but there were no distinct difference in sustentacular (type 2) cells from CB in these three species. Compared with lowland cattle, a small amount of nucleus heterochromatin of chief cells (type 1) in CB in migrated cattle increased. Some of chief cells exhibited anomalies in morphology. Intracytoplasmic organelles of chief cells were mostly swelling and dissolved, which resulted in small remnant of organelle and dense core vesicles. The expression of HIF-1α, NOS, LEPR and EPO varied in CB in these three species, while the positive expression rate of EPO in CB from yak was below that from lowland cattle（P<0.05）. Conclusion High altitude does not cast significant influence on the size of CB and the amount of chief cells in CB of yak. There is a certain extent of convergence in the ratio of different types of chief cells in CB between yak and migrated cattle, but the functional system of the type 1 cells is damaged because of the hypoxia in migrated cattle, suggesting that migrated cattle are experiencing the process of acclimatizing themselves to high altitude. Chronic hypoxia may affect the EPO protein expression in the CB from yak and migrated cattle.