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本实验以二乙基亚硝胺诱发大鼠肝癌为动物模型,结合病理形态学研究了细胞增殖与组织特异代谢关键性酶ACT 及OCT,CPS_1活性的相互改变及其与癌变的关系,同时作了鼠肝发育过程中酶活性变化的比较研究。(1)根据DENA 引癌过程中酶活性CPS_Ⅰ/ACT,OCT/ACT 及ACT/CPS_Ⅰ,ACT/OCT 相对比值的变化,以及病理形态观察结果,DENA 引癌过程大致可分为三个阶段:喂DENA6周以内为单纯性增生期。此时期酶活性相对比值的改变是可逆的,与再生肝相似。第6周以后至16周为癌变期。此时期出现肝细胞异型性增生及癌变病灶。酶活性相对比值的改变是不可逆的。16周到30周为癌变细胞发展成为肝细胞癌期。(2)癌变过程中(喂DENA6周以后),OCT 及CPS_Ⅰ活性持续降低,同时ACT 活性持续增高。肝癌结节中OCT 及CPS_Ⅰ活性约为正常肝的10～20%,ACT 活性约为正常肝的2倍。癌变过程中这两类酶活性的相互改变与发育过程中的情况正好相反。在发育过程中,胚胎肝内OCT 及GPS_Ⅰ活性较成年水平低,而ACT 活性则较高。新生后CPS_Ⅰ及OCT 活性升高,同时ACT 活性降低。(3)肝与肝癌上述酶可能是相同的。因为酶活性的最适pH 和在聚丙烯酰胺凝胶电泳图上的分布都是一致的。肝与肝癌OCT 及ACT 的K_m 相同而V_m 不同,说明癌变过程中酶活性的变化,主要是由于酶蛋白量的改变。此外,肝癌线粒体的蛋白量减少,但OCT 及CPS_Ⅰ的比活性(单位/毫克线粒体蛋白)仍较正常肝线粒体的低。(4)讨论了增生和分化与癌变的关系。初步认为,肝细胞的癌变是反分化(分化逆转)问题,和正常分化一样系由于基因表现的改变,不一定包含基因结构的改变。就与癌变有关的细胞增殖和分化的矛盾而言,细胞增殖及其有关酶活性的增高,可能是癌变发生的基础,而组织特异功能及其关键性酶活性的降低,可能与癌变的关系更为密切。因此癌变的发生,可能是由于在细胞分裂过程中致癌物使肝细胞特异功能基因的调节控制失常,从而引起增生代谢与特异代谢关键性酶活性不可逆的改变,使之失去肝细胞增殖与特异功能的正常平衡,而代之以不受控制的增生,最后形成癌细胞。
In this experiment, diethylnitrosamine-induced rat liver cancer was used as an animal model. Combined with pathomorphology, the interaction between cell proliferation and tissue-specific metabolic enzymes ACT, OCT, and CPS_1 activity and its relationship with canceration were studied. A comparative study of changes in enzyme activity during rat liver development. (1) According to the changes of the relative activities of CPS_I/ACT, OCT/ACT, ACT/CPS_I, and ACT/OCT in the process of DENA cancer induction, and the observation of pathological morphology, the process of DENA cancer induction can be roughly divided into three stages: Within 6 weeks of DENA, it was a period of simple hyperplasia. The change in relative ratio of enzyme activity during this period is reversible, similar to that of regenerative liver. From the 6th week to the 16th week, the cancerous period. Hepatocyte dysplasia and cancerous lesions appeared during this period. The change in relative ratio of enzyme activity is irreversible. At weeks 16 to 30, cancerous cells develop into hepatocellular carcinoma. (2) During the course of carcinogenesis (6 weeks after feeding DENA), the activity of OCT and CPS_I continued to decrease while the ACT activity continued to increase. The activity of OCT and CPS_I in liver cancer nodules is approximately 10-20% of normal liver, and the activity of ACT is approximately twice that of normal liver. The mutual change of these two types of enzyme activity in the process of carcinogenesis is contrary to the situation during development. During development, embryonic intrahepatic OCT and GPS_I activity was lower than adulthood, while ACT activity was higher. After the newborn, CPS_I and OCT activity increased while ACT activity decreased. (3) The above enzymes may be the same for liver and liver cancer. This is because the optimum pH of the enzyme activity and the distribution on the polyacrylamide gel electrophoresis pattern are the same. Liver and liver cancers have the same Km of OCT and ACT and V_m is different, which indicates that the change of enzyme activity in the process of carcinogenesis is mainly due to the change of the amount of enzyme protein. In addition, the protein amount of liver mitochondria decreased, but the specific activity of OCT and CPS_I (units/mg of mitochondrial protein) was still lower than that of normal liver mitochondria. (4) The relationship between hyperplasia and differentiation and carcinogenesis was discussed. It is initially believed that the canceration of hepatocytes is an issue of reverse differentiation (reversal of differentiation), and the same as normal differentiation, due to changes in gene expression, does not necessarily include changes in gene structure. With respect to the contradiction of cell proliferation and differentiation associated with carcinogenesis, the increase of cell proliferation and related enzyme activities may be the basis of carcinogenesis, and the reduction of tissue specific function and its key enzyme activity may be related to the carcinogenesis. For closeness. Therefore, the carcinogenesis may be due to the abnormal control of liver cell specific functional genes caused by carcinogens in the process of cell division, resulting in irreversible changes in the key enzyme activities of the proliferation and metabolism, and the loss of hepatocyte proliferation and specific functions. The normal balance, and instead of uncontrolled proliferation, the final formation of cancer cells.