Glucocorticoids, particularly cortisol and corticosterone, are key homeostatic regulators during metabolic and endocrine adaptations including inflammatory responses. Besides the established response of total cortisol (TC) concentrations during inflammatory processes in dairy cows, we investigated changes of corticosterone, free cortisol (FC), and serum albumin as the main protein of unspecific cortisol binding, in response to an intramammary lipopolysaccharide (LPS) challenge. Furthermore, we evaluated relationships of glucocorticoid responses with concomitant alterations of metabolites and their endocrine regulators, insulin and glucagon. Blood samples of 10 multiparous Holstein dairy cows (26.8 ± 3.4 d in milk, previous lactation yield: 7,601 ± 938 kg; mean ± SD) were obtained every 30 min up to 5 h after the LPS instillation, and rectal temperature and heart rate were measured in parallel. Corticosterone was measured by enzyme immunoassay, TC by radioimmunoassay, and the proportion of FC by ultrafiltration. A mixed model was used to evaluate differences within the investigated parameters among selected time points (0, 3.5, and 5 h relative to the intramammary LPS administration). Rectal temperature increased up to 41.6 ± 0.1°C at 5 h after the LPS application. Concentrations of TC and corticosterone increased until 3.5 h, and the proportion of FC relative to TC more than doubled until 3.5 h after LPS administration. Serum albumin concentration was reduced at 5 h compared with initial values, whereas concentrations of insulin, glucagon, and glucose were increased after 5 h compared with 0 h. In conclusion, the stimulation of the immune system by the intramammary LPS administration is accompanied by distinct metabolic and endocrine changes. Corticosterone and TC concentrations react similarly in response to the LPS challenge and earlier compared with metabolic adaptations. The increased need of active cortisol is covered by both increased secretion and a higher percentage of FC.

糖皮质激素，尤其是皮质醇和皮质酮，是包括炎症反应在内的代谢和内分泌适应过程中的关键稳态调节剂。除了奶牛炎症过程中总皮质醇 (TC) 浓度的既定反应外，我们还研究了皮质酮、游离皮质醇 (FC) 和作为非特异性皮质醇结合主要蛋白质的血清白蛋白的变化，以响应乳房内脂多糖 (LPS) ） 挑战。此外，我们评估了糖皮质激素反应与伴随代谢物及其内分泌调节剂、胰岛素和胰高血糖素改变的关系。在 LPS 滴注后 5 小时内，每 30 分钟采集 10 头经产荷斯坦奶牛的血样（牛奶 26.8 ± 3.4 天，先前泌乳产量：7,601 ± 938 kg；平均值 ± SD），并同时测量直肠温度和心率。酶免疫法测定皮质酮，放射免疫法测定TC，超滤法测定FC的比例。使用混合模型来评估所选时间点（相对于乳房内 LPS 给药的 0、3.5 和 5 小时）之间研究参数的差异。应用 LPS 后 5 小时，直肠温度升高至 41.6 ± 0.1°C。TC 和皮质酮的浓度增加到 3.5 小时，并且 FC 相对于 TC 的比例增加了一倍多，直到 LPS 给药后 3.5 小时。与初始值相比，血清白蛋白浓度在 5 小时时降低，而胰岛素、胰高血糖素和葡萄糖的浓度在 5 小时后与 0 小时相比增加。综上所述，乳房内注射 LPS 对免疫系统的刺激伴随着明显的代谢和内分泌变化。皮质酮和 TC 浓度对 LPS 挑战的反应类似，并且与代谢适应相比更早。增加的分泌和更高比例的 FC 覆盖了对活性皮质醇的需求增加。