Study on the development of the short-term screening model for chemical carcinogenic agents and its application in relation to biliary tract cancer.

为了建立一种短期筛选胆道癌致癌物的方法，我们测定了MNNG、ENNG、MCA、DMN和AFB_1诱导的牛胆管上皮细胞的非程序DUA合成（UDS）。在不添加S9的情况下，MNNG和ENNG诱导UDS。MCA仅在添加S9时引起UDS。无论是否存在S9，DMN均不能诱导UDS。S9的存在增强了AFB_1对DNA的修复作用。而在人胆囊上皮细胞中，MCS和DMN即使在S9的作用下也能诱导UDS，表明人胆囊上皮细胞中存在MCS和DMN的激活系统。通过应用更敏感的碱性和中性洗脱技术，我们成功地证明了DNA单链断裂的牛胆管上皮细胞由这些代理商。因此，碱性和中性洗脱/原代胆道上皮细胞培养系统提供了一个器官特异性模型，而不是UDS检测化学药物对胆道的遗传毒性。磷脂酶A_2和溶血素在胰胆管合流异常时的胆管癌变过程中起重要作用，但两者均未引起明显的DNA链断裂，提示两者本身均不是胰胆管合流异常时胆管癌变的启动剂。

To develop a useful test for the short-term screening of carcinogenic agents in relation to biliary tract cancer we measured unscheduled DUA synthesis (UDS) in bovine bile duct epithelial cells in culture induced by MNNG, ENNG, MCA, DMN and AFB_1 which were used successfully in developing biliary tract neoplasms in experimental animals. MNNG and ENNG induced UDS without addition of S9. MCA elicited UDS only if S9 was added. Regardless of the presence or abscence of S9, DMN failed to induce UDS. DNA repair by AFB_1 was enhanced by the presence of S9. On the contrary in human gallbladder epithelial cells MCS and DMN induced UDS even in the abscence of S9 indicating the presence of activating system of MCS and DMN in human gallbladder epithelium. By applying more sensitive alkaline and neutral elution technique we successfully demonstrated DNA single-strand breaks by these agents in bovine bile duct epithelial cells. Thus alkaline and neutral elution/ primary biliary tract epithelial cell culture system provides an organ specific model than UDS for detecting genotoxicities of chemical agents to the biliary tract. Phospholipase A_2 and lysolecithin which are supposed to play a significant role in the carcinogenesis of the biliary tract in anomalous pancreatico-biliary duct union did not induce significant DNA strand breaks, which suggests neither of them is an initiator of the carcinogenesis by itself.