Fardel O, Ratanasavanh D, Loyer P, Ketterer B, Guillouzo A
Unité de Recherches Hépatologiques, Institut National de la Santé de la Recherche Médicale, Rennes, France.
Eur J Biochem. 1992 Apr 15;205(2):847-52. doi: 10.1111/j.1432-1033.1992.tb16849.x.
Expression of P-glycoprotein (P-gp), the product of multidrug resistance gene(s), was investigated in primary cultures of normal adult rat hepatocytes. Levels of P-gp mRNAs determined by Northern blotting and of P-gp measured by immunoblotting increased in parallel with time in culture. As in normal liver, P-gp was found to be localized on the membrane of bile canaliculus-like structures. This increased expression of P-gp was associated with decreased intracellular retention of doxorubicin, which could be restored by compounds such as verapamil and cyclosporin; doxorubicin (and also vincristine) was more cytotoxic to early than to late cultures. As in preneoplastic and neoplastic liver, overexpression of P-gp in cultured hepatocytes was associated with differential changes in drug-metabolizing enzymes, including increased glutathione S-transferase 7-7. Functional P-gp over-expression was observed in the absence of xenobiotic exposure or cell division; it could be linked to cellular stress occurring during cell isolation and plating. Increased expression of P-gp was blocked by actinomycin D, indicating its dependence on increased transcription, while cycloheximide led to a superinduction suggesting negative regulation by a protein factor.
在正常成年大鼠肝细胞原代培养物中，对多药耐药基因产物P-糖蛋白（P-gp）的表达进行了研究。通过Northern印迹法测定的P-gp mRNA水平以及通过免疫印迹法测定的P-gp水平随培养时间平行增加。与正常肝脏一样，发现P-gp定位于胆小管样结构的膜上。P-gp的这种表达增加与阿霉素细胞内潴留减少有关，维拉帕米和环孢菌素等化合物可使其恢复；阿霉素（以及长春新碱）对早期培养物的细胞毒性比对晚期培养物更大。与癌前和肿瘤性肝脏一样，培养的肝细胞中P-gp的过表达与药物代谢酶的差异变化有关，包括谷胱甘肽S-转移酶7-7增加。在没有异生物质暴露或细胞分裂的情况下观察到功能性P-gp过表达；它可能与细胞分离和平板接种过程中发生的细胞应激有关。放线菌素D可阻断P-gp表达的增加，表明其依赖于转录增加，而环己酰亚胺导致超诱导，提示存在蛋白质因子的负调控。
