Existence of a common precursor to ACTH and endorphin in the anterior and intermediate lobes of the rat pituitary.
Existence of a common precursor to ACTH and endorphin in the anterior and intermediate lobes of the rat pituitary.
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大鼠垂体前叶和中叶中存在促肾上腺皮质激素和内啡肽的共同前体。
DOI：
10.1002/jss.400080304
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发表时间：
1978
期刊：
影响因子：
--
通讯作者：
R. Mains
中科院分区：
文献类型：
--
作者：
B. Eipper;R. Mains
用十二烷基硫酸钠聚丙烯酰胺凝胶电泳分离大鼠垂体前叶和中后叶的提取物，并测定免疫活性ACTH和内啡肽。在两个脑叶中，免疫活性ACTH的主要形式的表观分子量分别为31，000（31 K）、20- 21 K、14 K和4.5K，免疫活性内啡肽的主要形式的表观分子量分别为31 K（与免疫活性ACTH的峰值一致）、13 K（一种β-LH样肽）和3.5K（一种β-内啡肽样肽）。然而，免疫活性的定量分布之间的各种形式之间的差异很大的叶。使用极端COOH-末端ACTH抗血清的测定表明，大鼠垂体前叶和中间叶中的31 K ACTH/内啡肽分子与小鼠垂体瘤细胞中的促ACTH/内啡肽分子相似。使用对小鼠促肾上腺皮质激素原/内啡肽分子的NH 2-末端非ACTH、非内啡肽片段（称为16 K片段）具有特异性的放射免疫测定法测定大鼠垂体提取物。除了在31 K和20- 21 K下检测物质外，16 K片段放射免疫测定法还在两个肺叶的提取物中检测到大量的表观分子量为16 K的交叉反应物质。这一结果还表明，大鼠31 K ACTH/内啡肽分子的结构和加工类似于小鼠肿瘤细胞pro-ACTH/内啡肽。从大鼠垂体前叶和中叶制备细胞悬液，并保持培养24小时。从两个脑叶分离的细胞将[3 H]苯丙氨酸结合到免疫沉淀的ACTH和内啡肽分子中。通过用ACTH和内啡肽抗血清进行连续免疫沉淀，可以直接证明单个分子（31 K ACTH/内啡肽）具有ACTH和内啡肽的抗原决定簇。分离的前叶和中叶细胞释放大量的31 K ACTH/内啡肽到培养基中。分离的中叶细胞合成并分泌相对大量的β-内啡肽样分子;分离的前叶细胞分泌显著量的β-LH样分子和β-内啡肽样分子。在分离的叶的提取物的免疫测定中观察到前叶和中叶组织之间的这些相同的定量差异，并且可能反映了共同前体的处理中的差异。通过与环AMP类似物和磷酸二酯酶抑制剂孵育，可以刺激分离的前叶细胞释放增加量的免疫可沉淀ACTH和内啡肽。
Extracts of rat anterior and intermediate-posterior pituitary were fractionated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and assayed for immunoactive ACTH and endorphin. In both lobes the major forms of immunoactive ACTH have apparent molecular weights of 31,000 (31K), 20--21K, 14K, and 4.5K, and the major forms of immunoactive endorphin have apparent molecular weights of 31K (coincident with the peak of immunoactive ACTH), 13K (a betaLPH-like peptide), and 3.5K (a beta-endorphin-like peptide). However, the quantitative distribution of immunoactivity among the various forms differs greatly between the lobes. Assays using an extreme COOH-terminal ACTH antiserum indicate that the 31K ACTH/endorphin molecule in rat anterior and intermediate pituitary is similar to the pro-ACTH/endorphin molecule from mouse pituitary tumor cells. A radioimmunoassay that is specific for the NH2-terminal non-ACTH, nonendorphin segment (referred to as 16K fragment) of the mouse pro-ACTH/endorphin molecule was used to assay extracts of rat pituitary. In addition to detecting material at 31K and 20--21K, the 16K fragment radioimmunoassay detects significant amounts of cross-reactive material with an apparent molecular weight of 16K in extracts of both lobes. This result also suggests that the structure and processing of the rat 31K ACTH/endorphin molecule is similar to that of mouse tumor cell pro-ACTH/endorphin. Cell suspensions were prepared from the anterior and intermediate lobes of the rat pituitary and maintained in culture for a 24-h period. The isolated cells from both lobes incorporate [3H] phenylalanine into immunoprecipitable ACTH- and endorphin-containing molecules. By sequential immunoprecipitation with ACTH and endorphin antisera, it is possible to demonstrate directly that a single molecule (31K ACTH/endorphin) has antigenic determinants for both ACTH and endorphin. Significant amounts of 31K ACTH/endorphin are released into the culture medium by isolated anterior lobe and intermediate lobe cells. The isolated intermediate lobe cells synthesize and secrete relatively large amounts of a beta-endorphin-like molecule; the isolated anterior lobe cells secrete significant amounts of both a betaLPH-like molecule and a beta-endorphin-like molecule. These same quantitative differences between anterior and intermediate lobe tissue were observed in immunoassays of extracts of the separated lobes and probably reflect differences in the processing of the common precursor. The isolated anterior lobe cells can be stimulated to release increased amounts of immunoprecipitable ACTH and endorphin by incubation with a cyclic AMP analog and a phosphodiesterase inhibitor.