In vitro binding of the carcinogen N-[methyl-^<14>C]-nitrosodimethylamine by algal dietary fibers and their role in reducing its bioaccumulation.

第一项研究旨在确定藻类膳食纤维（DF）是否在体外与致癌物N-[甲基-^<14>C]-亚硝基二甲胺（[^<14>C]- dmna）结合，以及含有藻类膳食纤维的饮食如何影响口服致癌物的生物积累。以宗教海带（Laminaria religiosa， LRP）粉叶和疣尾草（Gracilaria verrucosa）琼脂等8种海藻DF进行体外实验。纤维素粉（CP）作为对照DF。CP、LRP和琼脂对DMNA的体外结合率分别为初始剂量的0.28%、0.65%和0.21%。饲喂含有2% LRP或2%琼脂的日粮的大鼠在给药后3小时或24小时进行检查。口服摄入的DMNA在肝脏中的滞留量减少，这可能是因为在给药后3小时内肠道对DMNA的吸附量减少。藻类对DMNA的结合率与DF值无关，也与肠道对DMNA吸收减少的程度无关。第二项研究是为了验证纤维素（不溶于水）和聚葡萄糖（可溶于水）在减少致癌物质[^<14>C]-DMNA的生物积累方面的作用，在相同的体内实验系统中，使用小鼠。结果表明，与对照组小鼠相比，cp喂养小鼠在给药后1 h [^<14>C]-的生物蓄积显著减少。在给药后1 h以后的时间点，cp饲喂小鼠与对照组的生物蓄积差异随着时间的推移逐渐减小。结果表明，致癌物的吸收和代谢在给药后1小时内发生。对于多葡萄糖小鼠，除给药后24 h的血液外，没有明显减少[^<14>C]的摄取。

The first study was initiated to determine if algal dietary fibers (DF) bind the carcinogen N-[methyl-^<14>C]-nitrosodimethylamine ([^<14>C]-DMNA) in vitro and how bioaccumulation of orally-given carcinogen is affected by a diet containing algal DF.Eight kineds of algal DF, including powdered fronds of Laminaria religiosa (LRP) and agar (from Gracilaria verrucosa) were used in the in vitro test. Cellulose powder (CP) was used as a control DF.In vitro binding rates of DMNA by CP, LRP and agar were 0.28%, 0.65% and 0.21% of the initial dose, respectively. Rats fed a diet containing 2% LRP or 2% agar were examined at 3 h or 24 h after dosing. There was reduced retention of the orally-ingested DMNA in the liver, posibly because of reduced DMNA-adsorption from the intestinal tract earlier than 3 h after dosing. Binding rates of DMNA by algae were neither related to the DF values nor to the extent of reduction of DMNA-absorption from the intestinal tract.The second study was performed to verify the effects of cellulose (nsoluble in water) and of polydextrose (soluble in water), in reducing bioaccumulation of the carcinogen [^<14>C]-DMNA in the same in vivo experimental system, using mice. As the results, [^<14>C]-bioaccumelation in CP-fed mice remarkably reduced at 1 h after dosing, compared with that in control mice.In the time points later than 1 h after dosing, difference in the bioaccumulation between CP-fed mice and cntrols were decreased sowly as the time lapsed. The results suggest that absorption and metabolism of the carcinogen took lace within 1 h after dosing. As to polydextrosefed mice, there was no significant reductin of [^<14>C] uptake, except blood at 24 h after dosing.