Fowlkes J, Freemark M
Department of Pediatrics, Duke University Medical Center, Durham, North Carolina 27710.
J Cell Physiol. 1992 Jul;152(1):19-27. doi: 10.1002/jcp.1041520104.
To assess the roles of developmental factors in the regulation of sheep IGFBP production at the cellular level, we characterized and compared the IGFBPs released by fetal, postnatal, and maternal sheep skin fibroblasts in culture with those in fetal, postnatal, and maternal sheep plasma. Sheep fibroblasts produced seven IGFBPs: a 36.5-41 kDa protein induced in vitro by IGF-I, likely representing oIGFBP-3; a 28.5 kDa protein that reacted with antisera to human IGFBP-2, likely representing oIGFBP-2; 25 and 27 kDa proteins induced in fetal fibroblasts by IGF-I; a 22 kDa protein that was inhibited by IGF-I, likely representing oIGFBP-4; and 21 and 23 kDa proteins labelled only by IGF-II, suggesting their similarities to IGFBP-6. The developmental pattern of IGFBP production by sheep fibroblasts in culture was similar in several respects to that observed in sheep plasma. For example, relative amounts of the 21, 22, and 28.5 kDa IGFBPs exceeded that of the 36.5-41 kDa protein in early fetal fibroblast conditioned media and in fetal plasma, while the relative concentrations of the 36.5-41 kDa protein increased markedly during the perinatal period. Sheep plasma differed, however, in two major respects from fibroblast conditioned media: First, fetal, and to a far lesser extent maternal, plasma contained a 200 kDa IGF-II-selective BP, likely to be the circulating form of the IGF-II receptor; and second, plasma, unlike conditioned media, contained a 26 kDa IGFBP, likely to be oIGFBP-1. The results of our studies suggest that the production and release of IGFBPs by isolated sheep fibroblasts is regulated by developmental factors operative under in vitro culture conditions. The differences in the relative levels of IGFBPs in conditioned media from fetal, postnatal, and maternal sheep fibroblasts resemble in several respects the differences in the relative concentrations of the various IGFBPs in fetal, postnatal, and maternal sheep plasma. Thus, sheep fibroblasts provide a useful though imperfect model system by which to examine the nutritional and hormonal regulation of sheep IGFBP production at various developmental stages.
为了在细胞水平评估发育因子在调节绵羊胰岛素样生长因子结合蛋白（IGFBP）产生中的作用，我们对培养的胎儿、出生后和母羊皮肤成纤维细胞释放的IGFBP与胎儿、出生后和母羊血浆中的IGFBP进行了特性鉴定和比较。绵羊成纤维细胞产生七种IGFBP：一种36.5 - 41 kDa的蛋白，在体外由IGF - I诱导产生，可能代表oIGFBP - 3；一种28.5 kDa的蛋白，与抗人IGFBP - 2抗血清反应，可能代表oIGFBP - 2；胎儿成纤维细胞中由IGF - I诱导产生的25 kDa和27 kDa蛋白；一种22 kDa的蛋白，被IGF - I抑制，可能代表oIGFBP - 4；以及仅被IGF - II标记的21 kDa和23 kDa蛋白，表明它们与IGFBP - 6相似。培养的绵羊成纤维细胞产生IGFBP的发育模式在几个方面与在绵羊血浆中观察到的相似。例如，在早期胎儿成纤维细胞条件培养基和胎儿血浆中，21 kDa、22 kDa和28.5 kDa的IGFBP相对含量超过36.5 - 41 kDa蛋白，而在围产期36.5 - 41 kDa蛋白的相对浓度显著增加。然而，绵羊血浆在两个主要方面与成纤维细胞条件培养基不同：第一，胎儿血浆以及程度远低于母羊血浆中含有一种200 kDa的IGF - II选择性结合蛋白，可能是IGF - II受体的循环形式；第二，与条件培养基不同，血浆中含有一种26 kDa的IGFBP，可能是oIGFBP - 1。我们的研究结果表明，分离的绵羊成纤维细胞产生和释放IGFBP受体外培养条件下起作用的发育因子调节。胎儿、出生后和母羊成纤维细胞条件培养基中IGFBP相对水平的差异在几个方面类似于胎儿、出生后和母羊血浆中各种IGFBP相对浓度的差异。因此，绵羊成纤维细胞提供了一个有用但并不完美的模型系统，通过它可以研究绵羊在不同发育阶段IGFBP产生的营养和激素调节。
