Sastry B V, Jaiswal N, Owens L K, Janson V E, Moore R D
Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee.
J Pharmacol Exp Ther. 1988 Apr;245(1):72-80.
The activities of 2-(alpha-naphthoyl)ethyltrimethylammonium (alpha-NETA) and its beta-isomer (beta-NETA) were studied at various sites of the cholinergic system using isolated enzyme and organ systems. They were selective inhibitors (I50: alpha-NETA, 9 microM; beta-NETA, 76 microM) of choline acetyltransferase (ChA). The inhibition of ChA by both alpha- and beta-NETA was noncompetitive with acetylcoenzyme A or choline as the variable substrate. In these experiments, the inhibitor and both substrates were added simultaneously to the reaction medium, and short reaction times of 10 min were used to determine initial linear velocities. Under these experimental conditions in the presence of substrates, the degree of inhibition of ChA by alpha-NETA was independent of enzyme concentration indicating the reversibility of the inhibition. If ChA was incubated with alpha-NETA for 10 min in the absence of substrates, the degree of inhibition was higher and was not reversible by dialysis of the inhibited ChA. These observations indicate that alpha-NETA is a pseudo-reversible or slowly reversible inhibitor. Neither alpha- nor beta-NETA exhibited significant effects at muscarinic receptors, ganglionic nicotinic receptors, skeletal muscular nicotinic receptors, cholinesterases or carnitine acetyltransferase at concentrations which inhibited ChA. At concentrations higher than their I50 values to inhibit ChA, both antagonized the effects of acetylcholine (ED50: alpha-NETA, 70-80 microM; beta-NETA, 100 microM), histamine and KCl-induced contractions in the guinea pig longitudinal ileal muscle. At high concentrations, alpha-NETA activated acetylcholinesterase (EC50, 360 microM) and inhibited cholinesterase (EC50, 1100 microM).(ABSTRACT TRUNCATED AT 250 WORDS)
使用分离的酶和器官系统，研究了2-(α-萘甲酰基)乙基三甲基铵(α-NETA)及其β-异构体(β-NETA)在胆碱能系统不同部位的活性。它们是胆碱乙酰转移酶(ChA)的选择性抑制剂(I50：α-NETA为9微摩尔；β-NETA为76微摩尔)。α-NETA和β-NETA对ChA的抑制作用，对于作为可变底物的乙酰辅酶A或胆碱而言均为非竞争性抑制。在这些实验中，将抑制剂与两种底物同时加入反应介质中，并采用10分钟的短反应时间来测定初始线性速度。在这些存在底物的实验条件下，α-NETA对ChA的抑制程度与酶浓度无关，表明该抑制作用具有可逆性。如果在不存在底物的情况下将ChA与α-NETA孵育10分钟，抑制程度更高，且通过对受抑制的ChA进行透析不能使其逆转。这些观察结果表明，α-NETA是一种假可逆或缓慢可逆的抑制剂。在抑制ChA的浓度下，α-NETA和β-NETA在毒蕈碱受体、神经节烟碱受体、骨骼肌烟碱受体、胆碱酯酶或肉碱乙酰转移酶上均未表现出显著作用。在高于其抑制ChA的I50值的浓度下，二者均拮抗乙酰胆碱(ED50：α-NETA为70 - 80微摩尔；β-NETA为100微摩尔)、组胺和氯化钾诱导的豚鼠回肠纵肌收缩。在高浓度时，α-NETA激活乙酰胆碱酯酶(EC50为360微摩尔)并抑制胆碱酯酶(EC50为1100微摩尔)。(摘要截断于250字)
