迷走神経切断術のイヌ実験胃癌発生に及ぼす影響

Effects of Selective Gastric Vagotomy on Production of Gastric Cancer in Dogs Given N-methyl-N´-nitro-N-nitrosoguanidine

　ラットに高率に腺胃癌を発生させるN-メチル-N´-ニトロ-N-ニトロゾグアニジン（MNNG）は，イヌでも同様の経口投与により，胃癌を発生させることが確かめられ¹⁾²⁾，胃癌研究に大きな役割を果たすことが期待されている．しかし，このイヌMNNG胃癌の多くは，異型性の乏しい早期の分化型癌であり，漿膜に達する進行癌で，しかも転移形成を伴う例は稀である³⁾．一方MNNGはイヌの小腸にかなり高率に肉腫を発生させるため，胃癌が進行する以前に，イヌを死亡させることも欠点である⁴⁾⁵⁾．

　われわれは，イヌ胃癌発生を促進させる工夫の一つとして，1971年4月からMNNG投与開始前に胃の迷走神経を切断する方法を試みた．この論文では，迷切犬の2頭にのみ肺，肝への血行性転移を伴う進行胃癌の発生をみた成績⁷⁾⁸⁾を中心に，迷走神経切断術の効果をまとめ検討した．

　The influence of selective gastric vagotomy on the quantity and quality of the stomach cancers produced by N-methyl-N´-vitro-N-nitrosoguanidine (MN NG) in dogs is studied.

　Twenty dogs were given 50 μg/ml of MNNG solution as a drinking water for 12 months. In half of them selective gastric vagotomy had been performed two months before. The mean level of the maximal acid output stimulated by 2μg/kg of tetragastrin in vagotomy group was reduced to one-fourth of the control group.

　In all of the vagotomized dogs, gastric cancer induction was recognized, the number of cancer lesions ranging from one to ten per dog. On the contrary, gastric cancer was found in six out of nine non-vagotomized dogs. The mean cancerous lesions in the control and vagotomy group were 1.8 and 5.3, respectively. Six lesions with invasion to lymphatic vessels were found in the vagotomy group as compared with one lesion in the control group. Among these cancers, one lesion in the control and four lesions in the vagotomy group were found to be advanced cancer penetrating through the proper muscle.

　Two dogs in the vagotomy group had metastatic formation to the perigastric lymph nodes and liver. In addition, miliary lung metastases were seen in one of them. On the contrary, no metastasis was found in the control.

　Effectiveness of vagotomy on increasing the number of tumor production and promoting tumor growth was demonstrated in the gastric carcinogenesis of N-methyl-N´-nitro-N-nitrosoguanidine.