Okuda H, Potter B J, Blades B, McHugh T A, Jacobs L N, Berk P D
Department of Medicine, Polly Annenberg Levee Hematology Center, Mount Sinai School of Medicine, New York, NY.
Drug Metab Dispos. 1989 Nov-Dec;17(6):677-82.
To determine which individual parameters contribute to the increased bilirubin clearance which follows phenobarbital administration in the rat, dose response studies are being conducted relating changes in various aspects of bilirubin transport to the dose of phenobarbital administered. The relationships between phenobarbital dose, immunoreactive ligandin concentrations, and cytosolic glutathione-S-transferase (GSHT) enzymatic activities were determined in the 100,000g liver cytosol obtained from non-fasted male Sprague-Dawley rats, treated for 6 days (ip) with either phenobarbital at various doses ranging from 1 to 125 mg/kg/day or distilled water. Ligandin levels were measured by radioimmunoassay employing an antiserum which reacts with both GSHT-1 (Ya) and -2 (Yc) subunits. Ligandin concentration increased in a dose-dependent fashion, achieving a maximal observed value of 278% of control at the highest administered phenobarbital dose. Values were significantly elevated compared to controls at doses as low as 3 mg/kg/day. GSH-dependent delta 5-3-ketosteroid isomerase (KSI) activity, which reflects predominantly GSH transferase subunit 1, and GSHT activity against 1-chloro-2,4-dinitrobenzene (CDNB) also increased over the entire range of phenobarbital doses administered. Both of these enzymatic activities were highly correlated with immunoreactive ligandin levels (KSI: r = 0.89, p less than 0.005; GSHT (CDNB): r = 0.92, p less than 0.001). By contrast, GSHT activity against 1,2-dichloro-4-nitrobenzene (DCNB), which resides principally on GSHT subunits not present in ligandin, did not correlate significantly with measured ligandin concentrations. These studies indicate that phenobarbital is capable of inducing immunoreactive ligandin concentrations and related enzymatic activities at doses as small as 5% of those commonly employed to demonstrate this effect.
为了确定哪些个体参数导致大鼠服用苯巴比妥后胆红素清除增加，正在进行剂量反应研究，将胆红素转运各方面的变化与所给苯巴比妥的剂量联系起来。在从非禁食雄性斯普拉格-道利大鼠获得的100,000g肝脏胞液中，测定苯巴比妥剂量、免疫反应性配体蛋白浓度和胞质谷胱甘肽-S-转移酶（GSHT）酶活性之间的关系，这些大鼠腹腔注射（ip）不同剂量（1至125mg/kg/天）的苯巴比妥或蒸馏水，持续6天。采用与GSHT-1（Ya）和-2（Yc）亚基均反应的抗血清，通过放射免疫测定法测量配体蛋白水平。配体蛋白浓度呈剂量依赖性增加，在最高给药苯巴比妥剂量时达到对照值的278%的最大观测值。低至3mg/kg/天的剂量时，与对照相比，数值显著升高。主要反映谷胱甘肽转移酶亚基1的谷胱甘肽依赖性δ5-3-酮类固醇异构酶（KSI）活性以及针对1-氯-2,4-二硝基苯（CDNB）的GSHT活性，在所给苯巴比妥剂量的整个范围内也增加。这两种酶活性均与免疫反应性配体蛋白水平高度相关（KSI：r = 0.89，p < 0.005；GSHT（CDNB）：r = 0.92，p < 0.001）。相比之下，主要存在于配体蛋白中不存在的GSHT亚基上的针对1,2-二氯-4-硝基苯（DCNB）的GSHT活性与所测配体蛋白浓度无显著相关性。这些研究表明，苯巴比妥能够在低至通常用于证明此效应剂量5%的剂量下诱导免疫反应性配体蛋白浓度和相关酶活性。
