Weaver S A, Dixon W T, Schaefer A L
Department of Agricultural, Food, and Nutritional Science, and Agriculture and Agri-Food Canada, Lacombe Research Centre, Alberta.
J Anim Sci. 2000 May;78(5):1319-30. doi: 10.2527/2000.7851319x.
The objectives of the current experiment were to determine whether boars heterozygous for the mutation in skeletal ryanodine receptors (sRyR), known to cause porcine stress syndrome, differed from wild-type boars in hypothalamic-pituitary-adrenal axis (HPA) function. We have examined basal plasma ACTH, cortisol, and corticosteroid-binding globulin (CBG) concentrations; plasma ACTH and cortisol responses to a nose-snare stressor and at slaughter; dexamethasone suppression of plasma ACTH and cortisol concentrations; and glucocorticoid receptor (GR) density in the pituitary gland, hippocampus, hypothalamus, and frontal cortex. We have also examined carcass yields, composition, and meat quality to determine whether differences in HPA activity were accompanied by an increased incidence of meat quality characteristics associated with pale, soft, exudative (PSE) meat. Thirty boars either heterozygous or wild-type (n = 15 per genotype) for mutated sRyR were tested for HPA function at 7 mo of age. Heterozygous boars had lower basal plasma ACTH (P < .05) and cortisol (P < .04) concentrations. Integrated basal plasma ACTH and cortisol levels were also lower (P < .05 and P < .005, respectively). Genotype had no significant effect on basal CBG, stressor-induced (nose snare or slaughter) or dexamethasone suppression of plasma ACTH or cortisol concentrations. No differences in immunoreactive GR levels were found in the pituitary gland or any brain region examined. We did find a significant, negative correlation (r = -.62, P < .02) between peak (0800) basal plasma ACTH concentrations and hippocampal GR levels. The alterations in basal HPA function in heterozygous boars were accompanied by lighter body weights (P < .03), decreased carcass fat depth (P < .04), and increased carcass lean yields (P < .02). There was a higher incidence of meat quality characteristics associated with PSE meat in heterozygous boars indicated by higher carcass temperatures (P < .04) and meat brightness (P < .0001) with lower carcass pH at slaughter (P < .03) and after chilling (P < .003). In conclusion, we have found differences in basal and not stressor-induced HPA function between boars heterozygous and wild-type for mutated sRyR. This altered basal HPA activity was accompanied by an increased incidence of meat quality aspects associated with PSE meat in heterozygous boars.
当前实验的目的是确定骨骼肌兰尼碱受体（sRyR）发生突变的杂合公猪（已知会导致猪应激综合征）与野生型公猪在下丘脑 - 垂体 - 肾上腺轴（HPA）功能上是否存在差异。我们检测了基础血浆促肾上腺皮质激素（ACTH）、皮质醇和皮质类固醇结合球蛋白（CBG）的浓度；血浆ACTH和皮质醇对鼻夹应激源及屠宰时的反应；地塞米松对血浆ACTH和皮质醇浓度的抑制作用；以及垂体、海马、下丘脑和额叶皮质中糖皮质激素受体（GR）的密度。我们还检测了胴体产量、组成和肉质，以确定HPA活性的差异是否伴随着与苍白、柔软、渗水（PSE）肉相关的肉质特征发生率的增加。对30头sRyR突变的杂合或野生型公猪（每种基因型n = 15头）在7月龄时进行了HPA功能测试。杂合公猪的基础血浆ACTH（P <.05）和皮质醇（P <.04）浓度较低。基础血浆ACTH和皮质醇的综合水平也较低（分别为P <.05和P <.005）。基因型对基础CBG、应激源诱导（鼻夹或屠宰）或地塞米松对血浆ACTH或皮质醇浓度的抑制作用没有显著影响。在所检测的垂体或任何脑区中，未发现免疫反应性GR水平存在差异。我们确实发现基础血浆ACTH浓度峰值（0800）与海马GR水平之间存在显著的负相关（r = -.62，P <.02）。杂合公猪基础HPA功能的改变伴随着体重较轻（P <.03）、胴体脂肪深度降低（P <.04）和胴体瘦肉产量增加（P <.02）。杂合公猪中与PSE肉相关的肉质特征发生率较高，表现为屠宰时（P <.03）和冷却后（P <.003）胴体温度较高（P <.04）、肉亮度较高（P <.0001）以及胴体pH较低。总之，我们发现sRyR突变的杂合公猪与野生型公猪在基础HPA功能上存在差异，而非应激源诱导的HPA功能差异。这种基础HPA活性的改变伴随着杂合公猪中与PSE肉相关的肉质方面发生率的增加。
