Kuhlman G, Roth J A, Nissen S
Department of Animal Science, Iowa State University, Ames 50011.
Am J Vet Res. 1991 Mar;52(3):388-92.
Previous studies of the amino acid analogue, alpha-ketoisocaproate (KIC), indicate that it can stimulate lymphocyte blastogenesis and antibody responses of sheep. To determine whether KIC could overcome the effects of adrenocorticotropic hormone (ACTH)-induced lymphocyte suppression, 24 lambs were fed a control diet, a diet supplemented with 0.05% KIC, or a diet supplemented with 0.05% of the parent amino acid leucine. Immune status was monitored by determining lymphocyte blastogenic responsiveness to phytohemagglutinin-P (PHA), concanavalin A (conA), and pokeweed mitogen (PWM) and percentages of T-cell subsets in the blood, using monoclonal antibodies and a flow cytometer. Serum cortisol, insulin, and glucagon concentrations also were determined. After 60 days of consuming the respective diet, lambs were administered either saline solution or ACTH (100 IU) twice daily for 3 consecutive days. Administration of ACTH increased serum cortisol and insulin concentrations; however, no effects were seen for serum glucagon concentration. Compared with saline administration, ACTH administration significantly (P less than 0.05) suppressed mitogen-stimulated lymphocyte blastogenesis by approximately 50%, regardless of the mitogen used, and significantly (P less than 0.01) decreased the percentage of circulating T lymphocytes and decreased (P less than 0.01) the ratio of T4 to T8 cells. Lambs fed KIC had greater PHA- and conA-stimulated blastogenic responses and significantly (P less than 0.05) increased ratio of T4 to T8 cells in the blood, compared with lambs fed the leucine-supplemented diet or the control diet and given corresponding injections. These data indicate that ACTH decreased in vitro lymphocyte blastogenesis and altered the subset ratios of blood lymphocytes in sheep. These changes were partially prevented by feeding KIC.
先前对氨基酸类似物α-酮异己酸（KIC）的研究表明，它能刺激绵羊的淋巴细胞增殖和抗体反应。为了确定KIC是否能克服促肾上腺皮质激素（ACTH）诱导的淋巴细胞抑制作用，给24只羔羊分别喂食对照日粮、添加0.05% KIC的日粮或添加0.05%母体氨基酸亮氨酸的日粮。通过使用单克隆抗体和流式细胞仪测定淋巴细胞对植物血凝素-P（PHA）、刀豆蛋白A（conA）和商陆有丝分裂原（PWM）的增殖反应以及血液中T细胞亚群的百分比来监测免疫状态。还测定了血清皮质醇、胰岛素和胰高血糖素浓度。在食用相应日粮60天后，羔羊连续3天每天两次注射生理盐水或ACTH（100 IU）。注射ACTH可提高血清皮质醇和胰岛素浓度；然而，血清胰高血糖素浓度未见变化。与注射生理盐水相比，无论使用何种有丝分裂原，注射ACTH均显著（P<0.05）抑制有丝分裂原刺激的淋巴细胞增殖约50%，并显著（P<0.01）降低循环T淋巴细胞百分比，降低（P<0.01）T4与T8细胞的比例。与喂食添加亮氨酸日粮或对照日粮并接受相应注射的羔羊相比，喂食KIC的羔羊具有更强的PHA和conA刺激的增殖反应，且血液中T4与T8细胞的比例显著（P<0.05）升高。这些数据表明，ACTH降低了绵羊体外淋巴细胞增殖，并改变了血液淋巴细胞的亚群比例。喂食KIC可部分预防这些变化。
