Sperlágh Beáta, Vizi E Sylvester
Department of Pharmacology, Laboratory of Molecular Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Szigony u. 43, Budapest 1083, Hungary.
Neurochem Res. 2007 Nov;32(11):1978-89. doi: 10.1007/s11064-007-9458-y. Epub 2007 Aug 25.
Here, the extracellular interconversion of nucleotides and nucleosides was investigated in rat hippocampal slices and synaptosomes by an HPLC-UV technique. Adenosine 5'-triphosphate (ATP) was converted to adenosine 5'-diphosphate (ADP), adenosine 5'-monophosphate (AMP), adenosine, inosine, and hypoxanthine in the slices, whereas ADP elicited parallel and concentration-dependent formation of ATP and AMP. The specific adenylate kinase inhibitor diadenosine pentaphosphate decreased the rate of decomposition of ADP and inhibited the formation of ATP. No substantial changes in the interconversion of ADP to ATP and AMP were found in the presence of dipyridamole, flufenamic acid, the P2 receptor antagonist pyridoxal-5-phosphate-6-azophenyl-2',4'-disulphonic acid tetrasodium (PPADS), and the alkaline phosphatase substrate para-nitrophenylphosphate. Negligible levels of nucleotides were generated when uridine 5'-diphosphate (UDP), AMP or adenosine were used as substrates. Ecto-adenylate kinase activity was also observed in purified synaptosomes. In summary, we demonstrate the presence of an ecto-adenylate kinase activity in the hippocampus, which is a previously unrecognized pathway that influences the availability of purines in the central nervous system.
在此，我们运用高效液相色谱 - 紫外检测技术，对大鼠海马切片和突触体中核苷酸与核苷的细胞外相互转化进行了研究。在切片中，三磷酸腺苷（ATP）可转化为二磷酸腺苷（ADP）、一磷酸腺苷（AMP）、腺苷、次黄苷和次黄嘌呤，而ADP则引发ATP和AMP的平行且浓度依赖性生成。特异性腺苷酸激酶抑制剂五磷酸二腺苷降低了ADP的分解速率，并抑制了ATP的生成。在存在双嘧达莫、氟芬那酸、P2受体拮抗剂磷酸吡哆醛 - 5 - 磷酸 - 6 - 偶氮苯基 - 2',4' - 二磺酸四钠（PPADS）以及碱性磷酸酶底物对硝基苯磷酸的情况下，未发现ADP向ATP和AMP相互转化有显著变化。当以二磷酸尿苷（UDP）、AMP或腺苷作为底物时，生成的核苷酸水平可忽略不计。在纯化的突触体中也观察到了胞外腺苷酸激酶活性。总之，我们证明了海马中存在胞外腺苷酸激酶活性，这是一条此前未被认识的影响中枢神经系统中嘌呤可用性的途径。
