Purification and characterization of burst-promoting activity

红细胞生成需要两种不同的生长因子。促红细胞生成素（Ep）既促进晚期红前体细胞（CFU-E）的生长，也促进它们成熟为红细胞原细胞，在此过程中启动血红蛋白（Hb）的合成。另一个因素，促爆发活性（BPA）作用于早期前体细胞（BFU-E），并负责这些细胞分化为对Ep具有高反应性的CFU-E。本项目旨在从人源中纯化BPA，并探讨BPA和Ep两种因子对甲基纤维素培养的人外周血单个核细胞红系爆发集落形成的影响。从再生障碍性贫血患者的尿液中分离出Ep，去除Ep后的废液中发现BPA。对BPA进行大量纯化，制备出完全不含Ep的BPA。仅加入Ep就形成了红色的爆发。BPA的加入不仅增加了爆发的数量，而且大大减少了爆发形成所需的Ep量。培养物中单独存在双酚a不会导致爆发，但会导致不含血红蛋白的小菌落的生长。向这些小菌落中添加Ep导致红系爆发的形成。如果在BPA存在的情况下开始培养，可以延迟6天给药Ep，而不会减少爆发次数；在没有BPA的情况下，如果在培养开始时不提供Ep， BFU-E会迅速丢失。BPA比单独存在Ep时产生的脉冲更大。爆发中Hb的微量分析表明BPA增加了每次爆发的Hb量。这种增加不能完全用每次爆发细胞数量的增加来解释，而部分归因于Hb量的增加。每一个细胞。

Two distinct growth factors are needed for erythropoiesis. Erythropoietin (Ep) promotes both the growth of late erythroid precursor cells (CFU-E) and their maturation into proerythroblasts in which hemoglobin (Hb) synthesis is initiated. The other factor, burst-promoting activity (BPA) acts on the early precursor cells (BFU-E) and is responsible for differentiation of these cells into CFU-E with high responsiveness to Ep. This project was aimed at purifying BPA from a human source and exploring the effects of the two factors, BPA and Ep, on erythroid burst-colony formation of human peripheral blood mononuclear cells in methlycellulose cultures. Ep was isolated from the urine of patients with aplastic anemia and BPA was found in the resiue obtained after removal of Ep. Extensive purification of BPA yielded a preparation of BPA completely free from Ep. Reddish bursts were formed with the addition of Ep alone. Addition of BPA not only elevated the number of bursts but also grealty reduced the amount of Ep reqiured for burst formation. The presence of BPA alone in cultures did not permit bursts to form but did permit the growth of small colonies that did not contain Hb. Addition of Ep to these small colonies led to the formation of erythroid bursts. Administration of Ep to the culture could be delayed for 6 days without decreasing the number of bursts if the cultures were initiated in the presence of BPA; in the absence of BPA, BFU-E were repidly lost if Ep was not provided at the start of the culture. BPA produced larger bursts than those formed in the presence of Ep alone. Microassays of Hb in the bursts indicated that BPA increased the amount of Hb per burst. This increase could not be entirely explained by the augumentation in cell number per burst but was partly ascribable to the increased amount of Hb. per cell.