Beer H F, Frey L D, Rossetti I, Remy N, Maier A, Schubiger P A
Paul Scherrer Institute, Radiopharmacy Division.
J Recept Signal Transduct Res. 1995 Jan-Mar;15(1-4):581-93. doi: 10.3109/10799899509045241.
The compound Ro 43-0463 [N-(2-aminoethyl)-5-iodo-2-pyridinecarboxamide)] is the iodo-analogue of Lazabemid (Ro 19-6327). The latter is well known to bind site specifically with KD = 15.7 nmol/l to the enzyme monoamine oxidase type B (MAO-B) which it inhibits (IC50 = 2 10(-8) mol/l) time dependently and reversibly. Ro 43-0463 having an IC50 of 310(-8) mol/l was labelled with 123I as well as with 125I to get a tool for measuring the MAO-B distribution autoradiographically and in the human brain with SPET (Single Photon Emission Tomography). The halogen exchange reaction of the bromo-precursor (Ro 18-4950) in the presence of CuSO4 and ascorbic acid was applied. The reaction conditions were optimized, varying the parameters time (30 to 105 min), precursor concentration (1 to 3.5 mg) and temperature (130 to 200 degrees C). The purification of [123I/125I]-Ro 43-0463 was performed on HPLC (Lichrosorb RP-18, 5 mu m, 250 x 8 mm) with 0.36 M H3PO4/EtOH 97/3 and 0.01 M (NH4)2HPO4 (1.5 ml/min) as eluent. The labelling yield was found to range between 60 and 70%. The activity concentration ranged between 18.5 and 37 MBq/ml. Autoradiography with rat brain slices was performed using 5 nM [125I]-Ro 43-0463 in TRIS-buffer (pH 7.4) for 90 min at 20 degrees C. It showed a radioactivity pattern corresponding to the known distribution of MAO-B in the rat brain and proved, after displacement with L-Deprenyl (1 mu M), the high specificity of binding Ro 43-0463.
化合物Ro 43 - 0463 [N-(2 - 氨基乙基)-5 - 碘 - 2 - 吡啶甲酰胺]是拉扎贝米德（Ro 19 - 6327）的碘类似物。众所周知，后者能以KD = 15.7 nmol/l的解离常数特异性结合到B型单胺氧化酶（MAO - B）上，并以时间依赖性和可逆性方式抑制该酶（IC50 = 2×10(-8) mol/l）。IC50为3×10(-8) mol/l的Ro 43 - 0463用123I和125I进行标记，以获得一种通过放射自显影和单光子发射计算机断层扫描（SPET）在人脑中测量MAO - B分布的工具。应用了在硫酸铜和抗坏血酸存在下溴前体（Ro 18 - 4950）的卤素交换反应。对反应条件进行了优化，改变了时间（30至105分钟）、前体浓度（1至3.5毫克）和温度（130至200摄氏度）等参数。[123I/125I]-Ro 43 - 0463的纯化在高效液相色谱（Lichrosorb RP - 18，5μm，250×8毫米）上进行，以0.36 M磷酸/乙醇97/3和0.01 M磷酸氢二铵（1.5毫升/分钟）作为洗脱剂。标记产率在60%至70%之间。活性浓度在18.5至37 MBq/ml之间。使用5 nM [125I]-Ro 43 - 0463在TRIS缓冲液（pH 7.4）中于20摄氏度下对大鼠脑切片进行90分钟的放射自显影。结果显示出与大鼠脑中已知的MAO - B分布相对应的放射性模式，并在用L - 司来吉兰（1μM）置换后证明了Ro 43 - 0463结合的高特异性。
