遊離脂肪酸による下痢性員毒マウス試験偽陽性の発生評価

摘要

Midgut glands of bivalves are used for the mouse bioassay of diarrhetic shellfish poison (DSP). A large quantity of free fatty acids (FFAs) causes a false positive outcome in the assay. To examine whether this is likely to occus under conditions of actual use, we analyzed the contents of the FFAs in the enlarged midgut glands during gametogenesis of Japanese scallops Patinopecten yessoensis that had been caught at two points in Hunka Bay on March 27, 2006, because the content of FFAs may increase with activation of lipogenesis for gametogenesis. Fatty acids (Fas) were measured with fluorometric high-performance liquid chromatography after derivatization with 9-anthryldiazomethane. The total FFAs (14 : 0, 16 : 0, 18 : 0, 16 :1, 18: 1, 18 :4, 20: 5 and 22 : 6) represented 3.3-4.2 wt% of the lipid. The toxic FFAs accounted for 40-43 wt% of the total FFAs. Content of each FFA (18 :1, 2.7-5.0 mg/g lipid; 18 :4, tr.-2.0 mg/g; 20 :4, n.d.; 20 : 5, 8.0-9.1 mg/g and 22:6, 2.0-2.1 mg/g) was lower than the lethal dose tentatively calculated from the relative toxicity. It appears that the likelihood of FFAs causing false-positives in the mouse bioassay is low if the sample is fresh and is extracted immediately after homogenizing.%日本では食用二枚貝の下痢性貝毒検査法としてマウス毒rn性試験が行われている．マウス毒性試験は，通常の食用二rn枚貝の場合にはむき身のアセトン抽出物を，大型員の場合rnには中腸腺のアセトン抽出物を，3匹のマウスの腹腔内にrn投与し，マウスの生死を観察する検査法であり，24時間rn以内に2匹以上死亡した場合を陽性と判定する1）．「体重rn16～20gのマウスを24時間で死亡させる毒量」を1マウrnス単位（MU）と定義し，試験液の希釈投与と組み合わせるrnことで，下痢性貝毒の含有量の範囲を表記している．