Wecker L, Reinhardt R R
Department of Pharmacology, Louisiana State University Medical Center, New Orleans 70112.
J Neurochem. 1988 Jun;50(6):1945-51. doi: 10.1111/j.1471-4159.1988.tb02501.x.
The main objective of these studies was to determine whether adenosine inhibits choline kinase in rat striata, leading to a decreased incorporation of choline into phosphorylcholine, a mechanism that may mediate seizure-induced increases in the levels of free choline in brain. Incubation of particulate and soluble fractions of striatal synaptosomes with adenosine or its metabolically stable analogues significantly inhibited enzyme activity. The inhibition was noncompetitive versus choline and competitive versus MgATP. Inhibitor constants for adenosine, 2-chloroadenosine, and 2',5'-dideoxyadenosine at the MgATP site were 94, 49, and 207 microM, respectively; these values were less than the Michaelis constant for MgATP (340 microM). To determine whether adenosine altered the phosphorylation of choline in an intact preparation, synaptosomes were incubated with [3H]choline in the presence or absence of adenosine or its analogues and the amount of [3H]-phosphorylcholine formed from the [3H]choline taken up was measured. All compounds tested significantly reduced the synthesis of [3H]phosphorylcholine. Results suggest that following seizures or hypoxia, when levels of adenosine increase and the concentration of ATP decreases, inhibition of choline phosphorylation may be manifest, resulting in increased levels of free choline in brain.
这些研究的主要目的是确定腺苷是否抑制大鼠纹状体中的胆碱激酶，从而导致胆碱掺入磷酸胆碱的量减少，这一机制可能介导癫痫发作引起的脑内游离胆碱水平升高。将纹状体突触体的微粒体和可溶性部分与腺苷或其代谢稳定类似物一起孵育，可显著抑制酶活性。这种抑制作用对胆碱是非竞争性的，对MgATP是竞争性的。腺苷、2-氯腺苷和2'，5'-二脱氧腺苷在MgATP位点的抑制常数分别为94、49和207微摩尔；这些值小于MgATP的米氏常数（340微摩尔）。为了确定腺苷是否在完整制剂中改变胆碱的磷酸化，将突触体在有或没有腺苷或其类似物的情况下与[3H]胆碱一起孵育，并测量由摄取的[3H]胆碱形成的[3H]磷酸胆碱的量。所有测试的化合物均显著降低了[3H]磷酸胆碱的合成。结果表明，在癫痫发作或缺氧后，当腺苷水平升高而ATP浓度降低时，胆碱磷酸化的抑制作用可能会显现出来，导致脑内游离胆碱水平升高。
