Biological and immunological characterization of cleaved and 16K forms of rat prolactin.
Biological and immunological characterization of cleaved and 16K forms of rat prolactin.
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DOI：
10.1210/endo-122-6-2892
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发表时间：
1988-06
期刊：
影响因子：
4.8
通讯作者：
C. Clapp;P. Sears;D. Russell;J. Richards;Brett K. Lev Ay-Young;C. S. Nicoll
中科院分区：
文献类型：
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作者：
C. Clapp;P. Sears;D. Russell;J. Richards;Brett K. Lev Ay-Young;C. S. Nicoll
据报道，大鼠PRL的切割形式（rPRL）存在于垂体中，并且是其靶组织的PRL蛋白水解的主要产物。一个16 K片段来自切割的PRL（cPRL）在体内大鼠乳腺有丝分裂活性，我们发现，切割和16 K PRL都能够结合到肝PRL受体。为了分析切割的PRL和16 K PRL的功能意义，通过在体外将24 K rPRL与25，000 X g大鼠乳腺团块一起孵育来产生足量的cPRL。将cPRL还原（2-巯基乙醇），并通过凝胶过滤分离16 K和8 K片段。通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳建立裂解和16 K样品的纯度，并测定它们的促有丝分裂[鸽子作物囊，Nb 2淋巴瘤细胞和乳腺细胞生物测定（BA）]，催乳（酪蛋白BA）和免疫（PRL RIA）活性。cPRL具有与完整PRL相同的促有丝分裂活性，但免疫活性只有完整PRL的一半。16 K片段在所有测定中均具有生物活性。其估计的促有丝分裂和催乳效力分别为24 K PRL的65%和10%，并且其免疫活性仅为完整激素的2%。因此，16 K片段具有比切割的或完整的24 K PRL更高的BA与RIA比率。16 K PRL的功能意义可能被低估，由于其低RIA活性。
A cleaved form of rat PRL (rPRL) has been reported to exist in the pituitary gland and to be the main product of PRL proteolysis by its target tissues. A 16K fragment derived from cleaved PRL (cPRL) has mammary mitogenic activity in rats in vivo, and we found that both cleaved and 16K PRLs are capable of binding to hepatic PRL receptors. To analyze the functional significance of cleaved and 16K PRLs, ample amounts of cPRL were generated by incubation of 24K rPRL in vitro with a 25,000 X g rat mammary gland pellet. cPRL was reduced (2-mercaptoethanol), and the 16K and 8K fragments were separated by gel filtration. The purity of the cleaved and 16K samples was established by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and their mitogenic [pigeon crop-sac, Nb2 lymphoma cell, and mammary cell bioassays (BAs)], lactogenic (casein BA), and immunologic (PRL RIA) activities were determined. cPRL had the same mitogenic activity, but half the immunoactivity, as intact PRL. The 16K fragment was biologically active in all assays. Its estimated mitogenic and lactogenic potencies were 65% and 10% those of the 24K PRL, respectively, and it had only 2% the immunoactivity of the intact hormone. Thus, the 16K fragment had higher BA to RIA ratios than cleaved or intact 24K PRLs. The functional significance of 16K PRL may have been underestimated owing to its low RIA activity.