ワカサギの後胚発生過程における直腸上皮細胞の形態的・機能的変化〔英文〕
スポンサーリンク
概要
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Pinocytotic ingestion of protein molecules by rectal epithelium cells has been known to occur in teleost larvae and is supposed to have a nutritional role in digestion of food proteins. Morphological and functional changes in the rectal epithelium cells of pond smelt were investigated to clarify their nutritional role during postembryonic development. The ability of the rectal epithelium cells to ingest protein molecules appeared a few days after hatching, prior to the initiation of feeding. The ability increased thereafter and was maintained for about 200 days till the immature stage of the fish. Throughout this period active pinocytotic features at the base of microvilli characterized the cells. Large supranuclear vacuoles appeared after the commencement of feeding. Food proteins, detected as a homogeneous electron-dense substance, filled the vacuoles of fed larvae. After the stage of gastric gland differentiation, at approximately 50 days, food proteins as well as the large supranuclear vacuoles tended to disppear from the cells. Although the cells retained the ability to ingest protein, no food protein was detected in the cells of juveniles about 80 days old which had functional stomachs. The cells of adult fish did not ingest protein molecules. They showed some invaginations of intermicrovillous plasma membranes but no supranuclear vacuoles. It was concluded that the rectal epithelium cells of larval pond smelt function in protein protein digestion from the stage of initiation feeding up until gestric gland differentiation.