Lubega G W, Prichard R K
Institute of Parasitology of McGill University, Macdonald College, Sainte Anne de Bellevue, Québec, Canada.
Mol Biochem Parasitol. 1990 Jan 15;38(2):221-32. doi: 10.1016/0166-6851(90)90025-h.
The specific (high-affinity) binding of tritiated benzimidazole [(3H]BZ) anthelmintics-mebendazole [(3H]MBZ) and oxibendazole [(3H]OBZ) to, and the specific displacement (inhibition) of these radioligands by unlabelled BZs (oxibendazole, mebendazole, oxfendazole, albendazole, fenbendazole and thiabendazole) from crude tubulin extracts prepared from thiabendazole (TBZ)-susceptible (S) or TBZ-resistant (R) strains of adult Haemonchus contortus, have been examined. The most striking difference between R and S was that the drug specifically bound at infinite ligand concentration (Bmax), was markedly reduced for the R strain, with no apparent change in association constant (Ka). Thus, resistance was associated with a loss of high-affinity receptors. TBZ-resistance was not associated with a change in low-affinity binding. There was a greater loss of high affinity receptors for [3H]OBZ than for [3H]MBZ. Using the displacement data. BZs were ranked according to their Ka and IC50 (concentration of BZ inhibiting 50% of radioligand binding) values. The Ka and IC50 values and the rank order of the BZs were approximately independent of the radioligand displaced or source (S or R) of the tubulin extracts used. The results are consistent with tubulin binding being the primary mechanism of action for all of these BZs.
已对氚化苯并咪唑[（3H）BZ]驱虫药——甲苯咪唑[（3H）MBZ]和奥苯达唑[（3H）OBZ]与来自噻苯达唑（TBZ）敏感（S）或TBZ耐药（R）成年捻转血矛线虫株制备的粗微管蛋白提取物的特异性（高亲和力）结合，以及未标记的BZs（奥苯达唑、甲苯咪唑、奥芬达唑、阿苯达唑、芬苯达唑和噻苯达唑）对这些放射性配体的特异性置换（抑制）进行了研究。R株和S株之间最显著的差异在于，在无限配体浓度（Bmax）下药物的特异性结合，R株明显降低，而缔合常数（Ka）无明显变化。因此，耐药性与高亲和力受体的丧失有关。TBZ耐药性与低亲和力结合的变化无关。与[（3H）MBZ]相比，[（3H）OBZ]的高亲和力受体丧失更多。利用置换数据，根据BZs的Ka和IC50（抑制50%放射性配体结合的BZ浓度）值对其进行排序。BZs的Ka和IC50值以及排序顺序大致与所置换的放射性配体或所用微管蛋白提取物的来源（S或R）无关。结果表明微管蛋白结合是所有这些BZs的主要作用机制。
