Simpson R B, Chase C C, Spicer L J, Carroll J A, Hammond A C, Welsh T H
Agricultural Research Service, USDA, Brooksville, FL 34601-4672, USA.
Domest Anim Endocrinol. 1997 Nov;14(6):367-80. doi: 10.1016/s0739-7240(97)00042-8.
To determine the effect of breed and estradiol-17 beta on selected hormones and metabolites, ovariectomized (> or = 3 mo) Angus (n = 14) and Brahman (n = 12) cows were paired by age and body weight and randomly assigned as either nonimplanted controls (CON) or implanted with estradiol (E2) for 45 d. After Day 7 and through Day 42, plasma concentration of somatotropin was greater for E2 than CON cows (treatment x day, P < 0.05). During an intensive blood sampling on Day 36, E2 cows tended (P < 0.10) to have greater somatotropin pulse amplitudes than CON cows, but other parameters of somatotropin release were not affected (P > 0.10) by E2 treatment. The effect of breed was apparent on Day 36 as Brahman cows had greater (P < 0.05) somatotropin pulse amplitude, basal secretion, and mean concentration than Angus cows. Overall, plasma concentration of IGF-I was greater (P < 0.01) for E2 than CON cows (158.3 vs. 104.2 ng/ml) and was greater for Brahman than Angus cows (164.1 vs. 98.4 ng/ml). However, there was a trend (P < 0.10) for a treatment x breed x day interaction for IGF-I (i.e., the magnitude of increase in IGF-I concentration was greater in E2-Angus than E2-Brahman cows). After Day 7 and through Day 42, total plasma IGF binding protein (IGFBP) activity was greater (P < 0.01) for E2 than CON cows. Ligand blotting revealed at least five forms of IGFBP activity, and E2 cows had greater (P < 0.05) binding activity of IGFBP-3 and the 30- and 32-kDa IGFBP than CON cows. Brahman cows had greater (P < 0.05) IGFBP-3 and the 32-kDa IGFBP than Angus cows. After Day 14 and through Day 42, concentration of urea nitrogen (PUN) was greater (P < 0.001) for CON than E2 cows (treatment x day, P < 0.001). Brahman had greater (P < 0.01) PUN than Angus cows (16.6 vs. 14.2 mg/dl). Plasma concentration of glucose was greater (P < 0.01) for E2 than CON cows (78.9 vs. 76.4 mg/dl) but was not affected (P > 0.10) by breed. In summary, these data suggest that some, but not all, of the positive effects of estradiol on peripheral concentration of IGF-I and IGFBP activity can be attributed to increased somatotropin. Moreover, breed influenced basal and E2-induced secretion of somatotropin and IGF-I such that differences between Brahman and Angus cows in plasma IGF-I concentrations were abated within 3 wk of estradiol implantation. Thus, breed influences the metabolite and hormonal response of cattle to estrogenic implants.
为确定品种和17β-雌二醇对所选激素及代谢产物的影响，将卵巢切除（≥3个月）的安格斯牛（n = 14）和婆罗门牛（n = 12）按年龄和体重配对，随机分为未植入对照组（CON）或植入雌二醇（E2）45天。在第7天之后直至第42天，E2组奶牛的生长激素血浆浓度高于CON组奶牛（处理×天数，P < 0.05）。在第36天进行密集采血时，E2组奶牛的生长激素脉冲幅度有高于CON组奶牛的趋势（P < 0.10），但E2处理对生长激素释放的其他参数没有影响（P > 0.10）。在第36天，品种的影响明显，婆罗门牛的生长激素脉冲幅度、基础分泌和平均浓度高于安格斯牛（P < 0.05）。总体而言，E2组奶牛的胰岛素样生长因子-I（IGF-I）血浆浓度高于CON组奶牛（P < 0.01）（158.3对104.2 ng/ml），婆罗门牛高于安格斯牛（164.1对98.4 ng/ml）。然而，IGF-I存在处理×品种×天数的交互作用趋势（P < 0.10）（即E2-安格斯牛的IGF-I浓度增加幅度大于E2-婆罗门牛）。在第7天之后直至第42天，E2组奶牛的总血浆胰岛素样生长因子结合蛋白（IGFBP）活性高于CON组奶牛（P < 0.01）。配体印迹显示至少有五种IGFBP活性形式，E2组奶牛的IGFBP-3以及30 kDa和32 kDa的IGFBP结合活性高于CON组奶牛（P < 0.05）。婆罗门牛的IGFBP-3和32 kDa的IGFBP高于安格斯牛（P < 0.05）。在第14天之后直至第42天，CON组奶牛的尿素氮（PUN）浓度高于E2组奶牛（处理×天数，P < 0.001）。婆罗门牛的PUN高于安格斯牛（P < 0.01）（16.6对14.2 mg/dl）。E2组奶牛的葡萄糖血浆浓度高于CON组奶牛（P < 0.01）（78.9对76.4 mg/dl），但不受品种影响（P > 0.10）。总之，这些数据表明，雌二醇对IGF-I外周浓度和IGFBP活性的一些（但不是全部）积极影响可归因于生长激素增加。此外，品种影响生长激素和IGF-I的基础分泌及E2诱导的分泌，使得婆罗门牛和安格斯牛血浆IGF-I浓度的差异在雌二醇植入3周内减弱。因此，品种影响牛对雌激素植入物的代谢和激素反应。
