Penclomedine (PEN) is a synthetic pyridine derivative that has been selected for clinical development based on its activity against human and mouse breast tumors implanted in mice. Its mechanism of action was unclear, and we were interested in determining its mechanism of cytotoxicity in vitro and in vivo. We found chromosome breaks, gaps, and exchanges in P388 ascites cells from BD2F1 mice treated with 200 mg/kg PEN. Maximal observed damage occurred 24 hr after drug administration. Alkaline elution indicated only limited DNA strand breaks and interstrand cross-linking. In vitro, PEN (75 micrograms/mL) inhibited RNA and DNA syntheses almost completely. In addition, incubation of [14C]PEN with rat liver S-9 fraction in the presence of calf thymus DNA resulted in the stable transfer of radioactivity to DNA. Addition of butylated hydroxytoluene, a free radical scavenger, to the incubation mixture inhibited the binding of drug to DNA, implicating free radicals as the ultimate reactive species. These data suggest that PEN can be metabolized to free radical, DNA-reactive products, and that its cytotoxicity is due to chromosomal damage produced by monofunctional alkylation. As an alternate mechanism, the ability of PEN to inhibit cellular dihydroorotate dehydrogenase was explored. Although PEN is an inhibitor of this enzyme in cells in vivo, in vitro, and in isolated cell sonicates, HPLC analyses of ribonucleotide triphosphate pools in P388 cells showed that all triphosphates had increased, especially UTP. Addition of uridine to the cell culture failed to prevent PEN-mediated cytotoxicity, suggesting that inhibition of de novo pyrimidine biosynthesis was not likely to be an important mechanism of action of this drug. These data suggest that PEN is activated in cells to a free radical that binds DNA.

中文翻译：

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潘氯丁定的生化药理学（NSC-338720）

Penclomedine（PEN）是一种合成的吡啶衍生物，基于其对植入小鼠中的人类和小鼠乳腺肿瘤的活性而被选择用于临床开发。其作用机理尚不清楚，我们感兴趣的是确定其在体内和体外的细胞毒性机理。我们发现用200 mg / kg PEN处理的BD2F1小鼠的P388腹水细胞中的染色体断裂，缺口和交换。给药后24小时观察到最大的损害。碱性洗脱表明仅有限的DNA链断裂和链间交联。在体外，PEN（75微克/毫升）几乎完全抑制了RNA和DNA的合成。此外，在小牛胸腺DNA存在的情况下，将[14C] PEN与大鼠肝脏S-9组分孵育会导致放射性向DNA的稳定转移。添加丁基化羟基甲苯，自由基清除剂对孵育混合物的抑制作用是抑制药物与DNA的结合，从而使自由基成为最终的反应物种。这些数据表明，PEN可以代谢为自由基，DNA反应产物，并且其细胞毒性是由于单官能烷基化产生的染色体损伤所致。作为另一种机制，探索了PEN抑制细胞二氢乳清酸脱氢酶的能力。尽管PEN在体内，体外和分离的细胞超声中是该酶的抑制剂，但是HPLC分析P388细胞中核糖核苷酸三磷酸池的结果显示，所有三磷酸均增加，特别是UTP。向细胞培养物中添加尿苷未能阻止PEN介导的细胞毒性，提示从头抑制嘧啶的生物合成不太可能是该药物的重要作用机理。这些数据表明，PEN在细胞中被激活成与DNA结合的自由基。