Wise T, Klindt J
U.S. Department of Agriculture, Agricultural Research Service, Clay Center, Nebraska 68933-0166, USA.
Growth Dev Aging. 1995 Fall;59(3):139-48.
Elucidation of cause and effect relationships between gonadal and thymic function can be particularly challenging due to the complexity of interactions among various hormones on thymic function, many of which are largely unknown. To monitor gonadal-thymic interaction with the endocrine changes associated with maturity, bulls, steers, heifers, and ovariectomized heifers were slaughtered at 4, 6, 10, 12, or 14 months of age (n = 5-7/sex/age). Steers and ovariectomized heifers were castrated before 1 week of age. Thymic weights were increased in castrated animals as early as 4 months of age (p < 0.01), and differences were more pronounced in males. Thymic secretory peptide, thymosin beta4, increased up to six months of age in all groups (p < 0.05) and then decreased with age, similar to the pattern of growth hormone. Prepuberal testosterone concentrations increased to 10-12 months of age and then decreased in both bulls and heifers (p < 0.05), coordinate with decreases of thymosin beta4 at 10 months of age. Growth hormone concentrations increased up to 6 months of age in all groups (p < 0.01) and then declined. Concentrations of prolactin peaked at 10 months of age (p < 0.01) but were not different between groups. Relationships of luteinizing hormone (LH) were highly related to thymosin beta4 changes in heifers during maturation. Changes of thymosin beta4 and LH were coordinate in ovary-intact heifers and inversely related in ovariectomized heifers. Gonadal effects on thymic weight were evident as early as 4 months of age, and no abrupt declines in thymic weight were detected at puberty.
由于多种激素对胸腺功能的相互作用十分复杂，其中许多作用在很大程度上尚不明确，因此阐明性腺与胸腺功能之间的因果关系可能极具挑战性。为了监测性腺 - 胸腺相互作用以及与成熟相关的内分泌变化，分别在4、6、10、12或14月龄宰杀公牛、阉牛、小母牛和去势小母牛（每组性别/年龄的样本量n = 5 - 7）。阉牛和去势小母牛在1周龄前进行去势。早在4月龄时，去势动物的胸腺重量就增加了（p < 0.01），且雄性的差异更为明显。胸腺分泌肽胸腺素β4在所有组中均在6月龄前升高（p < 0.05），然后随年龄下降，这与生长激素的模式相似。青春期前，公牛和小母牛的睾酮浓度在10 - 12月龄时升高，然后下降（p < 0.05），与10月龄时胸腺素β4的下降相一致。所有组的生长激素浓度在6月龄前升高（p < 0.01），然后下降。催乳素浓度在10月龄时达到峰值（p < 0.01），但各组之间无差异。在小母牛成熟过程中，促黄体生成素（LH）与胸腺素β4的变化高度相关。在未去势的小母牛中，胸腺素β4和LH的变化是协同的，而在去势小母牛中则呈负相关。性腺对胸腺重量的影响早在4月龄时就很明显，在青春期未检测到胸腺重量的突然下降。
