Désautés C, Sarrieau A, Caritez J C, Mormède P
Institut National de la Santé et de la Recherche Médicale, Institut National de la Recherche Agronomique, Institut François Magendie, Bordeaux, France.
Domest Anim Endocrinol. 1999 May;16(4):193-205. doi: 10.1016/s0739-7240(99)00014-4.
Six-wk-old piglets of both sexes from European Large White (LW, n = 36) and Chinese Meishan (MS, n = 24) breeds were individually exposed to a novel environment, a stressful stimulation. Behavioral and pituitary-adrenal reactivity were investigated. When compared with LW, MS pigs displayed low locomotion (18.5 +/- 2.2 vs. 41.0 +/- 3.8 squares crossed/10 min; P < 0.0001), and defecation scores (0.58 +/- 0.15 vs. 4.86 +/- 0.37 fecal boli; P < 0.0001). Basal concentrations of cortisol were higher in MS (96.1 +/- 1.1 vs. 44.9 +/- 1.1 ng/ml; P < 0.0001), although no differences between breeds were found in basal concentrations of adrenocorticotropic hormone (ACTH). In response to novel environment exposure, the ACTH increase was greater in LW than in MS, but the cortisol response was not different on a log scale. To further investigate the pituitary-adrenal differences between the two breeds, the 24-hr profile of ACTH and cortisol plasma concentrations, a corticotropin-releasing factor (CRF) and a coupled dexamethasone-ACTH test were studied. Five castrated male 9-wk-old piglets from each breed were fitted surgically with a jugular vein catheter. A classic marked circadian rhythm of cortisol and a weak nycthemeral variation of ACTH were found. Cortisol concentrations were approximately twice higher in MS exclusively during the early light phase (from 0800-1200 hr) of the cycle, but no significant interbreed difference was found in the circadian rhythm of ACTH. Administration of CRF (1 microgram/kg iv) induced the same significant increase in plasma ACTH and cortisol concentrations in both breeds. Administration of ACTH (10 micrograms/kg i.v.) increased significantly cortisol concentrations and revealed no difference in plasma cortisol response to ACTH. These data suggest that the hypercortisolism of MS pigs is of adrenal origin, and related to extrapituitary factors that control the adrenal sensitivity during the light phase of the diurnal cycle.
选用6周龄的欧洲大白猪（LW，n = 36）和中国梅山猪（MS，n = 24）的雌雄仔猪，将它们分别置于新环境中，这是一种应激刺激。对其行为和垂体 - 肾上腺反应性进行了研究。与大白猪相比，梅山猪的运动能力较低（每10分钟穿过的方格数为18.5±2.2 vs. 41.0±3.8；P < 0.0001），排便评分也较低（粪便团数为0.58±0.15 vs. 4.86±0.37；P < 0.0001）。梅山猪的皮质醇基础浓度较高（96.1±1.1 vs. 44.9±1.1 ng/ml；P < 0.0001），尽管两品种间促肾上腺皮质激素（ACTH）的基础浓度没有差异。在新环境刺激下，大白猪ACTH的增加幅度大于梅山猪，但对数尺度下皮质醇反应无差异。为进一步研究两品种间垂体 - 肾上腺的差异，对ACTH和皮质醇血浆浓度的24小时变化曲线、促肾上腺皮质激素释放因子（CRF）以及联合地塞米松 - ACTH试验进行了研究。每个品种选取5头9周龄去势雄性仔猪，通过手术在其颈静脉植入导管。发现皮质醇呈现明显的昼夜节律，而ACTH仅有微弱的昼夜变化。仅在昼夜周期的早期光照阶段（08:00 - 12:00时），梅山猪的皮质醇浓度约为大白猪的两倍，但ACTH的昼夜节律在两品种间无显著差异。静脉注射CRF（1微克/千克）后，两品种血浆ACTH和皮质醇浓度均有相同的显著升高。静脉注射ACTH（10微克/千克）后，皮质醇浓度显著升高，且两品种血浆皮质醇对ACTH的反应无差异。这些数据表明，梅山猪的高皮质醇血症源于肾上腺，且与控制昼夜周期光照阶段肾上腺敏感性的垂体外因素有关。
