Cryostat-cut sections of unfixed and formalin-fixed human pancreata obtained at autopsy were stained by the direct method with fluoresceinated antibodies to human gastrin I. The cytoplasm of a small population of cells in the islets of Langerhans exhibited a bright yellow-green fluorescence. Specificity of the inimunochemical reaction was indicated by a decrease in intensity of stain after preincubation of the fluoresceinated antibody with gastrin and after pretreating the section with nonfluoresceinated antibody-preparation. Immunological cross reactivity with cholecystokinin-pancreozymin was excluded by use of highly specific fluoresceinlabelled antibodies to human gastrin I which exhibit no binding of cholecystokinin-pancreozymin.
The presence of immunoreactive gastrin in the human pancreas was also demonstrated by radioimmunoassay measurements of pancreatic tissue extracts.
The gastrin-containing cells were selectively stained by the Hellerstrom-Hellman method, indicating that the gastrin cell of the pancreatic islet is the classical delta cell of Bloom (or A1 cell of Hellerstrom and Hellman).