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

Research Project

Project/Area Number	04671397
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	医学一般
Research Institution	Kitasato University School of Hygienic Sciences
Principal Investigator	YAMAMOTO Ichiro Kitasato University School of Hygienic Sciences Professor, 衛生学部, 教授 (10050361)
Co-Investigator(Kenkyū-buntansha)	MARUYAMA Hiroko Kitasato University School of Hygienic Sciences Lecturer, 衛生学部, 講師 (50129269)
Project Period (FY)	1992 – 1993
Project Status	Completed (Fiscal Year 1993)
Budget Amount *help	¥2,100,000 (Direct Cost: ¥2,100,000) Fiscal Year 1993: ¥600,000 (Direct Cost: ¥600,000) Fiscal Year 1992: ¥1,500,000 (Direct Cost: ¥1,500,000)
Keywords	algal dietary fiber / binding of carcinogen / cellulose / polydextrose / bioaccumulation / radio-labeled carcinogen / N-[methyl-^<14>C]-nitrosodimethylamine / 水溶性食物繊維 / 非水溶性食物繊維 / 食用海藻 / 海藻抽出物 / あまのり / ほそめこんぶ / DMNA
Research Abstract	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.