Floros J, Post M, Smith B T
J Biol Chem. 1985 Feb 25;260(4):2265-7.
Glucocorticoids accelerate fetal lung maturation by acting on the fetal lung fibroblast to induce the synthesis of fibroblast-pneumonocyte factor which in turn stimulates pulmonary surfactant synthesis by the alveolar type II cell. We have studied the site of glucocorticoid regulation of fibroblast-pneumonocyte factor synthesis in primary cultures of fetal rat lung fibroblasts. Conditioned media from fetal rat lung fibroblasts exposed to cortisol stimulate [Me-3H]choline incorporation into saturated phosphatidylcholine by primary cultures of fetal rat lung alveolar type II cells. This effect is blocked by the presence of actinomycin D during the first, but not the second, 24 h of incubation of the fibroblasts with cortisol. Cycloheximide blocks this effect if present during either the first or second 24 h of incubation. We fractionated mRNA from fetal rat lung fibroblasts incubated in the presence or absence of dexamethasone and observed that cell-free translation products from a fraction of approximately 500 bases possess biological activity in the bioassay. Such activity is only present in cell-free translation products of mRNA isolated from fibroblasts treated with dexamethasone. These results suggest that glucocorticoids act at a pretranslational level to induce production of fibroblast-pneumonocyte factor and that the primary translation products are biologically active.
糖皮质激素通过作用于胎儿肺成纤维细胞来加速胎儿肺成熟，诱导成纤维细胞 - 肺上皮细胞因子的合成，而该因子又刺激肺泡II型细胞合成肺表面活性物质。我们研究了糖皮质激素对原代培养的胎鼠肺成纤维细胞中成纤维细胞 - 肺上皮细胞因子合成的调节位点。来自暴露于皮质醇的胎鼠肺成纤维细胞的条件培养基可刺激胎鼠肺肺泡II型细胞原代培养物将[甲基 - ³H]胆碱掺入饱和磷脂酰胆碱中。在成纤维细胞与皮质醇孵育的第一个24小时而非第二个24小时期间，放线菌素D的存在会阻断这种作用。如果在孵育的第一个或第二个24小时期间存在环己酰亚胺，则会阻断这种作用。我们对在有或没有地塞米松存在的情况下孵育的胎鼠肺成纤维细胞的mRNA进行了分级分离，并观察到来自大约500个碱基部分的无细胞翻译产物在生物测定中具有生物活性。这种活性仅存在于从用地塞米松处理的成纤维细胞中分离的mRNA的无细胞翻译产物中。这些结果表明，糖皮质激素在翻译前水平起作用以诱导成纤维细胞 - 肺上皮细胞因子的产生，并且初级翻译产物具有生物活性。
