動物に発生した胃Carcinoidsについて

Gastric Carcinoids of Animal

　近年serotoninおよびその関連代謝産物，さらに症候学上の問題などの点でいわゆるcarcinoid tumorが漸次注目を集めつつあることは，周知のとおりである．ことにその組織発生に由来すると思われる腫瘍発生部位による組織化学的，発生病理学的，ひいては臨床病理学的な差については興味ある報告がみられている^2)7)8)25)．すなわち，前腸系由来の気管支・胃・上部十二指腸などに発生するcarcinoidはargyrophil細胞を主な構成成分とし，中腸系由来の小腸・虫垂などのcarcinoidはargentaffin細胞を主な構成成分とすることが多く^2)7)25)，flushingなどの臨床症状発現の面でもその差違が指摘されている⁸⁾²⁵⁾．

　筆者らの研究室で，1965年8月以来飼育中のMastomysに発生した最初の腺胃部腫瘍の組織像が人のcarcinoidに極めて類似していることは筆者らの注目をひくところであった．しかしその後に発生した数箇の腺胃部腫瘤は，明らかに悪性上皮性腫瘍の組織像を示していたが通常行なわれているargentaffin反応は常に陰性であり，一方電顕的には極めてまばらに散在する特殊な球形顆粒を見出してはいたが，組織化学上の陰性所見より結論がつかぬままに，検索をすすめていたところ，米国NIHで古くより当動物の自然発生腫瘍について，観察をつづけておられるK. C. Snellよりの私信¹⁸⁾でargyrophil反応を試みるよう示唆があり，その所見が電顕上の解決困難であった問題の解明に一つの前進を促す結果となった．今後，人のcarcinoidと臨床上の諸問題を解決する手がかりを得るためのモデル動物としてMastomysが大いに活用されることが期待される．

　Investigation of carcinoid tumors of man has recently become an area of renewed interest in the metabolism of the serotonin and its related substances along with histamine in relation to clinical manifestations. While the gastric carcinoids in man are rare, not more than 100 cases reported up to date, the African rodent, Praomy (Mastomys) natalensis, has recently been found to produce gastric carcinoids in a high incidence (Snell). Some characteristics of these tumors from our stock Mastomys are discussed with a special emphasis on pathogensis as to their argyrophil cell origin.

　Out of 130 malignant epithelial neoplasms from the glandular stomachs of Mastomys histologically confirmed, 71 that were identical to the remaining tumors were under the present study with reference to the argyrophil reaction. Of these 71 tumors, 43 (61%) showed a definitely positive argyrophil reaction(Sevier-Munger), while most of those tested were non-argentafiin. These tumors were therefore considered to be argyrophil cell carcinoicls.

　It is well known that most of gastric carcinoids of man are of argyrophil cell origin as well. While some silmilarities between carcinoids of man and those of Mastomys were found, some differences between these two were also encountered : as many as 52% of the former (Brodman, 1968) but none of the latter originated in the pyloric antrum and along the lesser curvature; the incidence of intragastric multiplicity was 41.5% in the latter in comparison with only 6.2% in the fomnel (Brodman).

　Specific secretory granules measuring 150 mμ to 250mμ in diameter surrounded by a typical wavy limiting membrane were also evident in these Mastomys tumors on the electron micrographs.

　It is emphasized that Mastomys may well be utilized for model experiments concerning the metabolic, symptomatologic and clinicopathologic analysis of the carcinoicl patients.