van der Kolk J H, Fouché N, Gross J J, Gerber V, Bruckmaier R M
Department of Clinical Veterinary Medicine, Swiss Institute for Equine Medicine (ISME), Vetsuisse Faculty, University of Bern and Agroscope, Bern 3012, Switzerland.
Department of Clinical Veterinary Medicine, Swiss Institute for Equine Medicine (ISME), Vetsuisse Faculty, University of Bern and Agroscope, Bern 3012, Switzerland.
Domest Anim Endocrinol. 2016 Jul;56 Suppl:S101-11. doi: 10.1016/j.domaniend.2016.02.008.
In this review, we address the function of the hypothalamus-pituitary-adrenocortical (HPA) axis with special emphasis on the comparison between the bovine and equine species. The pars intermedia of the pituitary gland is particularly well developed in horses and cattle. However, its function is not well appreciated in cattle yet. The Wulzen's cone of the adenohypophysis is a special feature of ruminants. Total basal cortisol concentration is much higher in horses than that in cows with similar free cortisol fractions. Corticotropin-releasing factor (CRF) concentrations in equine pituitary venous blood are lower compared with other species, whereas plasma ACTH concentrations in cows are higher than those in horses. A CRF challenge test induced a more pronounced cortisol response in horses compared with cattle, whereas regarding ACTH challenge testing, the opposite seems true. Based on data from literature, the bovine species is characterized by relatively high basal blood CRF and ACTH and low cortisol and glucose concentrations. Obviously, further lowering of blood cortisol in cattle is easily prevented by the high sensitivity to ACTH, and as a consequence, subsequent increased gluconeogenesis prevents imminent hypoglycemia. Hypoglycemia is less likely in horses given their high muscle glycogen content and their relatively high cortisol concentration. When assessing HPA axis reactivity, response patterns to exogenous ACTH or CRH might be used as a reliable indicator of animal welfare status in cows and horses, respectively, although it is emphasized that considerable caution should be exercised in using measures of HPA activity solely to assess animal welfare.
在本综述中，我们探讨下丘脑 - 垂体 - 肾上腺皮质（HPA）轴的功能，特别强调牛和马这两个物种之间的比较。垂体中间部在马和牛中特别发达。然而，其在牛中的功能尚未得到充分认识。腺垂体的伍尔岑氏锥体是反刍动物的一个特殊特征。马的基础皮质醇总浓度比具有相似游离皮质醇分数的奶牛高得多。与其他物种相比，马垂体静脉血中的促肾上腺皮质激素释放因子（CRF）浓度较低，而奶牛的血浆促肾上腺皮质激素（ACTH）浓度高于马。与牛相比，CRF激发试验在马中诱导出更明显的皮质醇反应，而关于ACTH激发试验，情况似乎相反。根据文献数据，牛的特点是基础血液CRF和ACTH相对较高，而皮质醇和葡萄糖浓度较低。显然，由于对ACTH高度敏感，牛血液皮质醇的进一步降低很容易被阻止，因此，随后糖异生增加可防止即将发生的低血糖。鉴于马的肌肉糖原含量高且皮质醇浓度相对较高，马发生低血糖的可能性较小。在评估HPA轴反应性时，对外源性ACTH或CRH的反应模式可能分别用作奶牛和马动物福利状况的可靠指标，尽管需要强调的是，仅使用HPA活性指标来评估动物福利时应格外谨慎。
