DRUG TRANSFER AND EXPRESSION OF P-GLYCOPROTEIN IN THE RAT 9L GLIOMA

将1.5×10~(-5)的9L胶质瘤细胞接种于大鼠脑内2周后，在第一次脑循环中用液体闪烁计数器测量放射性标记药物向脑内的转移量，并用Oldendorf法进行分析。用抗P-糖蛋白的单抗C-219也研究了与药物外排有关的P-糖蛋白的表达。用常规和免疫电子显微镜观察了脑毛细血管、肿瘤血管和胶质瘤细胞的超微结构。蔗糖(对照)，已知通过血脑屏障的运输是饱和的，在肿瘤中积累到比大脑高5倍的水平。MCNU(雷尼莫斯汀：甲基6-[3-(2-chloroethyl-3-nitrosoureido]-6-deoxy-alpha-D-glucopyranoside)，，5-氟尿嘧啶，5-FU，5-氟尿嘧啶)和阿霉素(阿霉素)在正常脑内的蓄积很少，而阿诺明(Nimustine：1-(4-氨基-2-甲基-5-嘧啶)甲基-3-(2-氯乙基)-3-亚硝脲盐酸盐)在正常脑内的蓄积增加。MCNU和阿霉素虽然扩散到肿瘤间质，但在胶质瘤细胞中的积聚可以忽略不计。相反，ACNU和5-FU在肿瘤细胞中的蓄积增加。在体外培养的9L胶质瘤细胞中，5-FU的转运可被ATP抑制剂或低温所抑制。虽然脑毛细血管内皮细胞和胶质瘤细胞膜均呈P-糖蛋白免疫组织化学阳性，但肿瘤血管中P-糖蛋白表达较低。超微结构显示肿瘤血管内皮细胞开窗增多、肿胀、连接破坏。因此，我们认为，亲水性药物，如阿霉素，被P-糖蛋白泵出，不会像其他亲脂性药物如ACNU或5-FU那样在9L胶质瘤中蓄积，这与载体介导的机制有关。

Two weeks after the inoculation of 1.5x10^5 of 9L glioma cells into the rat brain, the transfer of radiolabelled drugs into the brain and the experimental 9L glioma during the first cerebral circulation,was measured with a liquid scintilation counter and analyzed by the method of Oldendorf. The expression of P-glycoprotein, which is known to be associated with the efflux of drugs, was also studied, using anti-P-glycoprotein monoclonal antibody: C-219. Furthermore, the ultrastructure of brain capillaries, tumor vessels and glioma cells was studied by conventional and immuno-electron microscopy. Sucrose (control), the transport of which through the blood-brain barrier is known to be saturable, accumulated to 5 fold higher levels in the tumor relative to brain. MCNU (ranimustine: methyl 6-[3-(2-chloroethyl-3-nitrosoureido]-6-deoxy-alpha-D-glucopyranoside), 5-FU (5-fluorouracil) and doxorubicin (Adriamycin) showed quite little accumulation into the normal brain, whereas ACNU (nimustine: 1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride) showed an increased accumulation. MCNU and doxorubicin showed negligible accumulation in the glioma cells despite diffusion into the tumor interstitial space. In contrast, ACNU and 5-FU showed an increased accumulation in tumor cells. The transfer of 5-FU into the cultured 9L glioma cells was decreased by ATP inhibitors or by low temperature. Although both brain capillary endothelial cells and glioma cell membranes were immunohistochemically positive for P-glycoprotein, the tumor vasculature showed low expression of P-glycoprotein. The endothelial cells of tumor vessels ultrastructurally showed increased fenestrations, swelling and disrupted junctions. Accordingly, it is suggested that hydrophilic drugs such as doxorubicin, being pumped out by P-glycoprotein, do not accumulate in 9L glioma as do other lipophilic drugs such as ACNU, or 5-FU associated with the carrier-mediated mechanism.