Canalis E, Centrella M, McCarthy T L
Department of Research, Saint Francis Hospital and Medical Center, Hartford, Connecticut 06105.
Endocrinology. 1991 Nov;129(5):2457-62. doi: 10.1210/endo-129-5-2457.
Although bone matrix is a rich source of insulin-like growth factor-II (IGF-II), little is known about the regulation of its synthesis by bone cells. This is due in part to the lack of simple and reliable assays to measure IGF-II. We have developed a method to dissociate IGF-II from its binding proteins by acidification and ultrafiltration, and quantitated IGF-II by RIA in 24- to 72-h cultures of 21-day-old fetal rat calvariae. The coefficient of variation of the assay was 13.8% or less; the recovery of IGF-II was 30-50%, and IGF-I cross-reacted 1% or less in the assay compared to IGF-II standards. The IGF-II concentrations in calvarial culture medium were in the 1- to 3-nM range, and these levels were suppressed by cycloheximide (3.6 microM) by almost 80%. Continuous treatment with placental lactogen, PTH, GH, insulin, or T3 did not modify IGF-II concentrations in 24- to 72-h cultures. Treatment with 17 beta-estradiol, testosterone, and 1,25-dihydroxyvitamin D3 also had no effect on IGF-II levels, whereas cortisol (10-100 nM) decreased IGF-II concentrations by 20-50%. Transforming growth factor-beta, prostaglandin E2, and platelet-derived growth factor BB did not alter IGF-II levels, and basic fibroblast growth factor (0.06-6 nM) for 72 h decreased calvarial IGF-II by 30-50%. In conclusion, 21-day-old fetal rat calvariae secrete IGF-II, and its concentration in culture medium is decreased by cortisol and basic fibroblast growth factor.
尽管骨基质是胰岛素样生长因子-II（IGF-II）的丰富来源，但关于骨细胞对其合成的调节却知之甚少。部分原因是缺乏简单可靠的检测IGF-II的方法。我们开发了一种通过酸化和超滤将IGF-II与其结合蛋白解离的方法，并通过放射免疫分析法（RIA）对21日龄胎鼠颅骨进行24至72小时培养后的IGF-II进行定量。该检测方法的变异系数为13.8%或更低；IGF-II的回收率为30%-50%，与IGF-II标准品相比，IGF-I在该检测中的交叉反应率为1%或更低。颅骨培养基中的IGF-II浓度在1至3 nM范围内，这些水平被环己酰亚胺（3.6 microM）抑制了近80%。在24至72小时培养中，连续用胎盘催乳素、甲状旁腺激素、生长激素、胰岛素或三碘甲状腺原氨酸处理并没有改变IGF-II的浓度。用17β-雌二醇、睾酮和1,25-二羟维生素D3处理对IGF-II水平也没有影响，而皮质醇（10-100 nM）使IGF-II浓度降低了20%-50%。转化生长因子-β、前列腺素E2和血小板衍生生长因子BB并没有改变IGF-II水平，而碱性成纤维细胞生长因子（0.06-6 nM）处理72小时使颅骨IGF-II降低了30%-50%。总之，21日龄胎鼠颅骨分泌IGF-II，其在培养基中的浓度会被皮质醇和碱性成纤维细胞生长因子降低。
