Giros B, Llorens-Cortes C, Gros C, Schwartz J C
Peptides. 1986 Jul-Aug;7(4):669-77. doi: 10.1016/0196-9781(86)90043-4.
Using a sensitive radioimmunoassay, the tripeptide Tyr-Gly-Gly (YGG) which corresponds to the N-terminal sequence of opioid peptides was detected in rat brain and identified by HPLC. Its regional distribution paralleled that of (Met5)enkephalin (YGGFM), a marker of enkephalin neurons. Ablation of these neurons in the striato-pallidal pathway by intrastriatal kainate, induced a significant decrease in YGG levels in caudateputamen and globus pallidus (-49%), consistent with the hypothesis that YGG originates from enkephalin neurons. When pallidal slices were incubated under various conditions, YGG was mainly found in the incubation medium indicating a predominantly extracellular localization. Depolarization of these slices by a K+-stimulus elicited a release of YGGFM accompanied by a marked increase in YGG levels. Bestatin and amastatin further enhanced YGG levels, reflecting the participation of aminopeptidases in the metabolism of the tripeptide and its precursor. Captopril, an inhibitor of the angiotensin-converting enzyme (ACE) showed no effect on the recovery of YGGFM and YGG. In contrast, the formation of YGG was completely prevented by Thiorphan (IC50 value = 9 nM) and phosphoramidon, two inhibitors of "enkephalinase" (EC 3.4.24.11; membrane metallo-endopeptidase), thus identifying the latter as the YGG-forming enzyme. The K+-induced increase in YGG + YGGFM levels in medium containing bestatin exceeded by about 60% the amount of YGGFM released from tissues, suggesting that YGG was mainly formed by extracellular hydrolysis of the various opioid fragments of the proenkephalin molecule. In vivo, YGG levels of cerebral regions were also markedly reduced in rats treated with acetorphan, a parenterally active "enkephalinase" inhibitor. All data suggest that YGG levels constitute an index of opioid peptide release.
采用灵敏的放射免疫分析法，在大鼠脑中检测到了与阿片肽N端序列相对应的三肽Tyr-Gly-Gly（YGG），并通过高效液相色谱法进行了鉴定。其区域分布与脑啡肽神经元的标志物（Met5）脑啡肽（YGGFM）的分布平行。纹状体内注射红藻氨酸破坏纹状体-苍白球通路中的这些神经元，导致尾状核和苍白球中的YGG水平显著降低（-49%），这与YGG源自脑啡肽神经元的假说一致。当在各种条件下孵育苍白球切片时，YGG主要存在于孵育培养基中，表明其主要定位于细胞外。用K+刺激使这些切片去极化，会引发YGGFM的释放，同时YGG水平显著升高。贝司他汀和氨肽酶抑制剂进一步提高了YGG水平，反映了氨肽酶参与了该三肽及其前体的代谢。血管紧张素转换酶（ACE）抑制剂卡托普利对YGGFM和YGG的恢复没有影响。相反，“脑啡肽酶”（EC 3.4.24.11；膜金属内肽酶）的两种抑制剂硫磷酰胺（IC50值 = 9 nM）和磷酰胺脒完全阻止了YGG的形成，从而确定后者为形成YGG的酶。在含有贝司他汀的培养基中，K+诱导的YGG + YGGFM水平升高比从组织中释放的YGGFM量高出约60%，这表明YGG主要是由脑啡肽原分子的各种阿片肽片段在细胞外水解形成的。在体内，用肠胃外活性“脑啡肽酶”抑制剂阿醋芬处理的大鼠，其脑区的YGG水平也显著降低。所有数据表明，YGG水平构成了阿片肽释放的一个指标。
