Mangino M M, Hollenberg P F, Scarpelli D G
Department of Pathology, Northwestern University Medical School, Chicago, IL 60611.
Carcinogenesis. 1988 Oct;9(10):1763-72. doi: 10.1093/carcin/9.10.1763.
The rates of uptake of the carcinogen N-nitrosobis(2-oxopropyl)amine (BOP) by hepatocytes isolated from Fischer rats and Syrian hamsters were determined in order to investigate species differences in cellular transport of the carcinogen. Initial rates of uptake of [1-14C]BOP by hepatocytes were measured using a rapid centrifugation technique. At cell densities from 1.5 to 6 x 10(6) cells/ml, initial rates of uptake were as much as 4-fold more rapid in hamster hepatocytes than in those of the rat. The cell/medium distribution ratio for hamster hepatocytes reached a value of 9.0 after a 20-min incubation with an extracellular BOP concentration of 20 microM. Under the same conditions, the cell/medium distribution ratio for rat hepatocytes was only 2.4. These results indicated that BOP uptake proceeded against a concentration gradient and was more rapid in hamster hepatocytes. In both species, the rates of uptake were saturable with increasing concentration (2-685 microM) and displayed biphasic kinetics characteristic of high-affinity (Km less than 20 microM) and low-affinity (Km greater than 30 microM) processes for the uptake of BOP. Evidence for the involvement of an ATP-dependent active carrier-mediated transport process was obtained from experiments in which hepatocytes were preincubated with metabolic inhibitors. Significant inhibition of uptake was observed in the presence of KCN, carbonyl cyanide-3-chlorophenylhydrazone, antimycin A, oligomycin and other agents which interfere with electron transport or ATP generation. Based on the reduction in uptake rates, rat hepatocytes were more sensitive to the effects of these inhibitors. These results suggest that the entry of BOP into hepatocytes is under cellular regulation and that the more rapid rate of uptake in liver cells of the hamster may be one factor responsible for the observation that BOP is a more potent hepatotoxin and carcinogen in this species.
为了研究致癌物在细胞转运方面的种属差异，测定了从Fischer大鼠和叙利亚仓鼠分离出的肝细胞对致癌物N-亚硝基双(2-氧代丙基)胺（BOP）的摄取速率。采用快速离心技术测量了肝细胞对[1-¹⁴C]BOP的初始摄取速率。在细胞密度为1.5至6×10⁶个细胞/毫升时，仓鼠肝细胞的初始摄取速率比大鼠肝细胞快达4倍。用20微摩尔/升的细胞外BOP浓度孵育20分钟后，仓鼠肝细胞的细胞/培养基分布比达到9.0。在相同条件下，大鼠肝细胞的细胞/培养基分布比仅为2.4。这些结果表明，BOP的摄取是逆浓度梯度进行的，并且在仓鼠肝细胞中更快。在两个物种中，摄取速率随着浓度增加（2至685微摩尔/升）而饱和，并显示出BOP摄取的高亲和力（Km小于20微摩尔/升）和低亲和力（Km大于30微摩尔/升）过程的双相动力学特征。通过肝细胞与代谢抑制剂预孵育的实验获得了ATP依赖的主动载体介导转运过程参与的证据。在存在KCN、羰基氰化物-3-氯苯腙、抗霉素A、寡霉素和其他干扰电子传递或ATP生成的试剂时，观察到摄取有显著抑制。基于摄取速率的降低，大鼠肝细胞对这些抑制剂的作用更敏感。这些结果表明，BOP进入肝细胞受细胞调节，并且仓鼠肝细胞中更快的摄取速率可能是BOP在该物种中是更强效的肝毒素和致癌物这一观察结果的一个因素。
