Dores R M, Truong T, Steveson T C
Department of Biological Sciences, University of Denver, Colorado 80208.
Gen Comp Endocrinol. 1992 Aug;87(2):197-207. doi: 10.1016/0016-6480(92)90023-d.
Steady-state analyses were performed on the proopiomelanocortin (POMC)-related end-products present in acid extracts of the pars intermedia of the anuran amphibian, Bombina orientalis. Sephadex G-75 gel filtration chromatography indicated that immunoreactive alpha-MSH-sized material and N-acetylated beta-endorphin-related material are the major POMC-related products present in this tissue. The alpha-MSH-sized immunoreactivity was further fractionated by reversed phase HPLC. The major peak of immunoreactivity isolated by this procedure eluted with the same retention time as synthetic ACTH(1-13)amide. Cation exchange chromatography supported the conclusion that the major storage form of alpha-MSH in the pars intermedia of Bombina is ACTH(1-13)amide. Analysis of Bombina pars intermedia in culture indicated that mono-acetylated and di-acetylated alpha-MSH were the major forms of alpha-MSH secreted into the medium. The major peak of N-acetylated beta-endorphin-related material was further analyzed by cation exchange chromatography and Sephadex G-25 gel filtration column chromatography. The major storage form of beta-endorphin in this tissue is N-acetylated, has a net positive charge at pH 2.75 of +1, and has an apparent molecular weight of 1.2K. The beta-endorphin present in the pars intermedia of this tissue does not undergo further N-acetylation at the time of secretion. These results indicate that in the pars intermedia of the archaeobatrachian, Bombina orientalis, the N-acetylation of alpha-MSH is a cosecretory processing event, whereas N-acetylation of beta-endorphin is a post-translational processing event. These results are compared to other archaeobatrachian and neobatrachian pituitary POMC systems that have been analyzed.
对东方铃蟾（一种无尾两栖动物）中间叶酸提取物中存在的促阿片-黑素细胞皮质素原（POMC）相关终产物进行了稳态分析。葡聚糖G-75凝胶过滤色谱表明，免疫反应性α-MSH大小的物质和N-乙酰化β-内啡肽相关物质是该组织中主要的POMC相关产物。通过反相高效液相色谱对α-MSH大小的免疫反应性进行了进一步分离。通过该方法分离出的主要免疫反应性峰与合成促肾上腺皮质激素（1-13）酰胺具有相同的保留时间。阳离子交换色谱支持了这样的结论，即东方铃蟾中间叶中α-MSH的主要储存形式是促肾上腺皮质激素（1-13）酰胺。对培养的东方铃蟾中间叶的分析表明，单乙酰化和二乙酰化α-MSH是分泌到培养基中的主要α-MSH形式。通过阳离子交换色谱和葡聚糖G-25凝胶过滤柱色谱对N-乙酰化β-内啡肽相关物质的主要峰进行了进一步分析。该组织中β-内啡肽的主要储存形式是N-乙酰化的，在pH 2.75时净正电荷为+1，表观分子量为1.2K。该组织中间叶中存在的β-内啡肽在分泌时不会进一步进行N-乙酰化。这些结果表明，在古蛙类东方铃蟾的中间叶中，α-MSH的N-乙酰化是一种共分泌加工事件，而β-内啡肽的N-乙酰化是一种翻译后加工事件。将这些结果与已分析的其他古蛙类和新蛙类垂体POMC系统进行了比较。
