Lang S, Sperk G
Department of Pharmacology, University of Innsbruck, Austria.
Regul Pept. 1995 May 30;57(2):183-92. doi: 10.1016/0167-0115(95)00031-6.
Preprotachykinin B (PPT-B) contains two peptide sequences which are flanked by pairs of dibasic amino acids: the decapeptide neurokinin B and a 30 amino acid non-tachykinin peptide consisting of the amino acids 50-79 of PPT-B. Whereas the existence of neurokinin B is well established in brain and peripheral tissues, native PPT-B(50-79) has not been identified so far. We have previously studied the distribution of PPT-B(50-79)-immunoreactivity in the rat brain using antibodies directed against synthetic PPT-B(50-79). Now we adapted a radioimmunoassay for characterizing neurochemically PPT-B(50-79)-immunoreactivity in the rat. In the brain concentrations ranging from 2 to 180 fmol/mg wet tissue weight were measured using synthetic PPT-B(50-79) as standard. The highest concentrations were observed in the interpeduncular nucleus and in the hypothalamus (180 and 90 fmol/mg tissue, respectively). Intermediate concentrations (15 to 60 fmol/mg tissue) were present in cortical areas, in the hippocampus, the spinal cord and in the olfactory bulb. Modest levels were detected in the cerebellum. Considerably lower concentrations of PPT-B(50-79)-immunoreactivity were observed in peripheral tissues. They were highest in the adrenal medulla and in the urinary bladder (3.0 and 1.2 fmol/mg tissue, respectively). This distribution, as observed by radioimmunoassay, correlated to that previously revealed by immunocytochemistry. Tissue concentrations of total PPT-B(50-79) immunoreactivity, however, were slightly higher than those of neurokinin B. Gel filtration chromatography on Sephadex G50 and reversed phase HPLC revealed at least three PPT-B(50-79) immunoreactive peaks. About 90% of the PPT-B(50-79)-immunoreactivity was contained within 2 peaks of apparently higher molecular weight than PPT-B(50-79). A minor portion of PPT-B(50-79)-immunoreactivity comigrated with the synthetic peptide, suggesting that only minor amounts of PPT-B(50-79) are formed in vivo. The processing enzyme(s) cleaving protachykinin B at the pair of basic amino acids (Lys80-Arg81) located between PPT-B(50-79) and neurokinin B may not be acting at the Arg48-Arg49 site (followed by -Leu50) at the amino terminal end of PPT-B(50-79).
前速激肽原B（PPT-B）包含两个由双碱性氨基酸对侧翼的肽序列：十肽神经激肽B和一个由PPT-B的50-79位氨基酸组成的30个氨基酸的非速激肽肽段。虽然神经激肽B在脑和外周组织中的存在已得到充分证实，但天然的PPT-B(50-79)迄今尚未被鉴定出来。我们之前使用针对合成的PPT-B(50-79)的抗体研究了大鼠脑中PPT-B(50-79)免疫反应性的分布。现在我们采用了一种放射免疫分析法来对大鼠脑中的PPT-B(50-79)免疫反应性进行神经化学特征分析。以合成的PPT-B(50-79)作为标准，在脑中测得的浓度范围为2至180 fmol/mg湿组织重量。在脚间核和下丘脑中观察到最高浓度（分别为180和90 fmol/mg组织）。皮质区域、海马体、脊髓和嗅球中存在中等浓度（15至60 fmol/mg组织）。在小脑中检测到的水平较低。在外周组织中观察到的PPT-B(50-79)免疫反应性浓度要低得多。它们在肾上腺髓质和膀胱中最高（分别为3.0和1.2 fmol/mg组织）。通过放射免疫分析法观察到的这种分布与先前通过免疫细胞化学揭示的分布相关。然而，总PPT-B(50-79)免疫反应性的组织浓度略高于神经激肽B的浓度。在Sephadex G50上进行凝胶过滤色谱和反相高效液相色谱显示至少有三个PPT-B(50-79)免疫反应性峰。约90%的PPT-B(50-79)免疫反应性包含在两个分子量明显高于PPT-B(50-79)的峰中。一小部分PPT-B(50-79)免疫反应性与合成肽共迁移，这表明体内仅形成少量的PPT-B(50-79)。在PPT-B(50-79)和神经激肽B之间位于碱性氨基酸对（Lys80-Arg81）处切割前速激肽原B的加工酶可能不在PPT-B(50-79)氨基末端的Arg48-Arg49位点（后面跟着-Leu50）起作用。
