The gastro-intestinal extract from which GIP was eventually purified was made from the duodenojejunal region of the pig. Cellular localization using indirect immunofluorescence studies indicated that the polypeptide was present in cells situated predominantly in the mid-zone of the glands in the duodenum and upper jejunum in both dog and man (Polak et al. 1973). Cells demonstrating positive immunofluorescence using guinea-pig antiporcine GIP serum and fluorescein-labelled sheep anti-guinea-pig IgG were more numerous than secretin cells found in similar areas. Cytochemical and other staining reactions characterized the GIP cell as lead haemotoxylin-positive, Grimelius-positive, non-argentaffin and weakly positive for tryptophan. It was considered to belong to that series of cells referred to by Pearse (1969) as the APUD cells or endocrine polypeptide cells. The GIP cell was tentatively considered, as a result of electron microscopy, to be the D1 cell because the distribution most closely matched the small granule-containing cell first described by Vassallo et al. (1971).
KeywordsGastric Inhibitory Polypeptide Enterochromaffin Cell Conventional Electron Microscopy Ileocaecal Junction APUD Cell
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