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10-羟基喜树碱(羟喜)是从我国南方特有植物喜树中分得的新抗癌有效成份。体外实验表明,不同浓度的羟喜(25～200μM)能程度不等地抑制小鼠肝癌细胞对胸苷和尿苷的转运。并能明显抑制[~3H]TdR或[~3H]UR掺入到DNA和RNA。若先用羟喜与癌细胞作用0.5小时,然后洗去药液,再观察对核苷转运的影响,发现羟喜对核苷转运的抑制是可逆的。体外实验还表明,羟喜对肝癌细胞胸苷激酶和尿苷激酶活力无明显的影响,这提示它抑制核苷转运的机制可能与核苷的磷酸化受抑无关。转运动力学的分析表明,小鼠肝癌细胞转运胸苷和尿苷的K_m值分别为0.53μM和13μM,V_(max)值分别为8.6和500pmol/分/10~6细胞。羟喜是竞争性抑制肝癌细胞对嘧啶核苷的转运。
10-Hydroxycamptothecin (Hydroxycamptothecin) is a new anti-cancer effective ingredient from Camptotheca acuminata, a unique plant in southern China. In vitro experiments showed that different concentrations of hydroxythiazole (25 ~ 200μM) can inhibit the transfer of thymidine and uridine in mouse liver cancer cells. And can significantly inhibit [~ 3H] TdR or [~ 3H] UR incorporation into DNA and RNA. If the first effect of 0.5 hours with hydroxyl hi and cancer cells, and then wash away the liquid, and then observe the effect on the transfer of nucleosides, found that the inhibition of hydroxy nucleoside on the transfer of nucleosides is reversible. In vitro experiments also showed that hydroxythiazide had no significant effect on the activity of thymidine kinase and uridine kinase in hepatoma cells, suggesting that its mechanism of inhibiting nucleoside transport may not be related to the inhibition of nucleoside phosphorylation. The analysis of transport kinetics showed that the Km values of the thymidine and uridine in mouse hepatoma cells were 0.53 μM and 13 μM, respectively, and the V max values were 8.6 and 500 pmol/min/10-6 cells, respectively. Hydroxy-hi competitively inhibits the translocation of pyrimidine nucleosides by hepatoma cells.