Oberbauer A M, Currie W B, Krook L, Thonney M L
Dept. of Anim. Sci., Cornell University, Ithaca, NY 14853-4801.
J Anim Sci. 1989 Nov;67(11):3124-35. doi: 10.2527/jas1989.67113124x.
The objective was to study control of mature size by characterizing metacarpal growth plate closure in relation to relevant bone growth-regulating hormones in two breeds exhibiting distinct differences in mature frame size. Thirty-four Suffolk and 34 Dorset ram lambs were slaughtered in pairs within breed at birth, weaning and monthly intervals until 420 d and then bimonthly to 600 d. Plasma growth hormone was depressed to undetectable levels due to the high-energy, ad libitum-fed diet. Plasma insulin-like growth factor-I (IGF-I) rose over the growth period from 116 ng/ml (newborn Suffolk) to a high of 451 ng/ml (420-d Dorset); it appeared to peak at approximately 400 d and then declined to a stable level. Dorsets consistently exhibited higher IGF-I levels. The thyroid hormones exhibited no apparent age association. An age-associated rise was detected for testosterone, but not for estradiol. Mature metacarpal lengths were estimated to be 147.2 and 127.4 mm for Suffolks and Dorsets, respectively. Ninety-five percent of mature length was attained in Suffolks by 226 d and in Dorsets by 165 d. Growth plates, however, did not begin to appear closed until 390 d and closure was not complete in all animals until 480 d, suggesting that metacarpal growth rate was dissociated temporally from growth plate closure. Although growth plate closure likely is controlled by the endocrine system, there were no apparent relationships between circulating hormones and growth plate width, age at closure or zonal divisions within the growth plate, suggesting that the growth plate experiences a very different hormonal environment than what can be measured in the circulating blood.
目的是通过表征掌骨生长板闭合情况以及与两种成熟体格大小存在明显差异的品种中相关骨生长调节激素的关系，来研究成熟大小的控制。34只萨福克公羊羔羊和34只多塞特公羊羔羊在出生时、断奶时以及每月一次（直至420天）、之后每两个月一次（直至600天）按品种成对屠宰。由于采用高能、随意采食的日粮，血浆生长激素被抑制到无法检测的水平。血浆胰岛素样生长因子-I（IGF-I）在生长期间从116 ng/ml（新生萨福克羊）升至最高451 ng/ml（420天的多塞特羊）；它似乎在约400天达到峰值，然后下降至稳定水平。多塞特羊的IGF-I水平始终较高。甲状腺激素未表现出明显的年龄相关性。检测到睾酮随年龄增加，但雌二醇没有。萨福克羊和多塞特羊的成熟掌骨长度估计分别为147.2毫米和127.4毫米。萨福克羊在226天达到成熟长度的95%，多塞特羊在165天达到。然而，生长板直到390天才开始出现闭合，所有动物直到480天才完全闭合，这表明掌骨生长速度在时间上与生长板闭合脱节。尽管生长板闭合可能受内分泌系统控制，但循环激素与生长板宽度、闭合年龄或生长板内的区域划分之间没有明显关系，这表明生长板所经历的激素环境与循环血液中可测量的激素环境非常不同。
