Abribat T, Lapierre H, Dubreuil P, Pelletier G, Gaudreau P, Brazeau P, Petitclerc D
Montreal University, Notre-Dame Hospital Research Center, Quebec, Canada.
Domest Anim Endocrinol. 1990 Jan;7(1):93-102. doi: 10.1016/0739-7240(90)90058-8.
Plasma insulin-like growth factor-I (IGF-I) concentrations were monitored in Holstein females through different periods of their growth, lactation and after acute or chronic growth hormone-releasing factor (GRF) administration. Plasma samples were radioimmunoassayed using a human IGF-I antibody after a 24 hr incubation in a HCl(.1N)-glycine(.2M) buffer (pH 2). In a first study, IGF-I concentrations were measured in Holstein females of different ages and(or) stages of lactation (n = 6 per group). The IGF-I concentrations in newborn calves (102.0 +/- 11.3 ng/ml) markedly decreased (P less than .01) in 1 mo old animals (50.2 +/- 7.1 ng/ml), then increased (P less than .01) to 137.0 +/- 5.1 and 137.4 +/- 11.0 ng/ml in 6 and 10 mo old heifers, respectively. In dairy cows, IGF-I concentrations were low 24 hr post-partum (44.7 +/- 7.6 ng/ml) and then increased (P less than .05) to remain stable throughout lactation (91.3 +/- 4.9, 92.8 +/- 12.9, 96.1 +/- 7.6, 90.7 +/- 8.8 ng/ml at 2, 3, 6 and 9 mo of lactation, respectively). There was a further increase (P less than .05) to 113.7 +/- 3.1 ng/ml during the dry period. In a second trial, blood samples were collected from lactating dairy cows every 2 hr for 24 hr following a sc injection of saline (n = 4) or human (h) GRF (1-29)NH2 (10 micrograms/kg BW, n = 4). The IGF-I peak concentration was reached on average 10 hr after the GRF injection and was higher (P less than .01) in treated cows than in control cows (135.4 vs 86.9 +/- 16.2 ng/ml). In the last trial, daily sc injections of 10 micrograms of hGRF(1-29)NH2 per kg BW to dairy cows (252 days of lactation) for 57 days, which increased milk production by 14% (2 kg/day), also increased (P less than .01) IGF-I concentration: 127.1 +/- 5.3 and 118.0 +/- 1.6 vs 90.7 +/- 4.7 and 96.0 +/- 5.0 ng/ml on days 29 and 57 of treatment for treated (n = 9) and control (n = 8) cows, respectively. Thus, the IGF-I concentration in dairy cattle varies with age and stage of lactation, and is increased by GRF administration in lactating dairy cows.
在荷斯坦奶牛不同生长阶段、泌乳期以及急性或慢性给予生长激素释放因子（GRF）后，监测其血浆胰岛素样生长因子-I（IGF-I）浓度。血浆样本在含0.1N盐酸和0.2M甘氨酸的缓冲液（pH 2）中孵育24小时后，使用人IGF-I抗体进行放射免疫分析。在第一项研究中，测量了不同年龄和（或）泌乳阶段的荷斯坦奶牛（每组6头）的IGF-I浓度。新生犊牛的IGF-I浓度（102.0±11.3 ng/ml）在1月龄动物中显著降低（P<0.01）至（50.2±7.1 ng/ml），然后在6月龄和10月龄小母牛中分别升高（P<0.01）至137.0±5.1和137.4±11.0 ng/ml。在奶牛中，产后24小时IGF-I浓度较低（44.7±7.6 ng/ml），然后升高（P<0.05），并在整个泌乳期保持稳定（泌乳2、3、6和9个月时分别为91.3±4.9、92.8±12.9、96.1±7.6、90.7±8.8 ng/ml）。干奶期进一步升高（P<0.05）至113.7±3.1 ng/ml。在第二项试验中，对泌乳奶牛皮下注射生理盐水（n = 4）或人（h）GRF（1-29）NH2（10微克/千克体重，n = 4）后，每2小时采集一次血样，共采集24小时。GRF注射后平均10小时达到IGF-I峰值浓度，且处理组奶牛的峰值浓度高于对照组奶牛（P<0.01）（135.4对86.9±16.2 ng/ml）。在最后一项试验中，对泌乳252天的奶牛每天皮下注射10微克/千克体重的hGRF(1-29)NH2，持续57天，使产奶量提高了14%（2千克/天），同时也使IGF-I浓度升高（P<0.01）：处理组（n = 9）和对照组（n = 8）奶牛在治疗第29天和第57天的IGF-I浓度分别为127.1±5.3和118.0±1.6对90.7±4.7和96.0±5.0 ng/ml。因此，奶牛的IGF-I浓度随年龄和泌乳阶段而变化，并且在泌乳奶牛中给予GRF可使其升高。
