Ethylnitrosourea経胎盤誘発脳腫瘍における発癌プロモーターの作用—第1報：ラット胎児脳細胞のin vitro malignant transformationに対する促進効果

EFFECT OF TUMOR PROMOTING AGENTS ON THE IN VITRO MALIGNANT TRANSFORMATION OF THE FETAL RAT BRAIN CELLS EXPOSED IN UTERO TO ETHYLNITROSOUREA

　抄録　発癌プロモーターである12-0—tetradecanoyl phorbol 13—acetate （TPA）およびphenobarbital（PB）の胎児ラット脳細胞のin vitro悪性変化に及ぼす影響をin vivo-in vitro分析法を用いて険討を行った。in vivoでのENU投与は，妊娠18日目SD-JCLラットの腹腔内に，　ENU （50 mg／kg）を投与し，その72時間後に胎児脳細胞を分離して培養系に移した。TPAは，0.1ng／ml−50.0 ng／mlの種々濃度で，PBは，1.0mM−5.0mMの種々濃度で，初代培養時より，培養液に添加した。形態学的には，TPA添加ENU処理群では，　ENU処理群に比べ約90日早期に"piled up focus"が出現した。軟寒天上でのコロニー形成能の検討では，TPA添加ENU処理群では，　ENU処理群に比べ，約110日早期に有意なplat—ing efficacyの上昇を認めた。　Con A凝集能の結果もコロニー形成能と同様に，　TPA添加ENU処理群において早期のCon A凝果能の亢進が認められた。　in vivoへの可移植性の結果も同様に，　TPA添加ENU処理群において，約90日早期に可移植性が獲得された。以上の結果より，　TPAがENUを経胎盤的に投与されたラット胎児脳細胞に対して，　in vitroでの悪性変化を促進することが示唆された。

The potent tumor promoter 12-0-tetradecanoyl phorbol 13-acetate (TPA) and phenobarbital (PB) were tested for their abilities to promoting effect of these agents on the in vitro malignant trans-formation of the fetal rat brain cells exposed in utero to Ethylnitrosourea (ENU). Rat fetal brain cells were transfered to cultured system at 72 hours after single pulse of ENU (50 mg/kg B. W.) to pregnant SD-JCL rats on the 18th day of ges-tation. Primary cultured cells were divided into 20 groups, and graded doses of PB from 1. 0 mM to 5.0 mM or that of TPA from 0. 1 ng/ml to 50. 0 ng/ml were added continuously into cultured me-dium. In the ENU group treated with TPA, it was found the results of more early appearance of "piled up focus" for about 90 days, more early capacity of colony formation in semisolid soft agar for about 110 days, and more early appearance of tumorigenicity for about 90 days than that in the ENU groups treated with or without acetone. And increased agglutinability to Concanavalin A (200 itg/ml) was appeared more early in the ENU groups treated with TPA than in the ENU groups. On the basis of these results, it is suggested that TPA promoted the in vitro malignant transforma-tion of the fetal rat brain cells with a transpla-cental carcinogen of ENU, and TPA might effect as a tumor promoter on the neurogenic carcinoge-nesis. As for the mechanisms of the promoting effect of TPA, it is speculated that TPA might modulate the function of cell membrane from the results of Concanavalin A agglutinability, and might modulate the differentiation on cell function from the results of morphological analysis.