ZINC AND MANGANESE CONTENTS OF MICRO-DISSECTED PANCREATIC ISLETS OF SOME RODENTS

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Abstract
By a flameless atomic absorption spectrophotometry procedure, using a graphite furnace, it was possible to assay the contents of Zn and Mn in micro-dissected pancreatic islets of several rodents. Interest was focused upon the islets of guinea-pigs, due to the fact that guinea-pig insulin lacks a histidine residue in the B10 position of the molecule which normally binds Zn (or other heavy metals) in the hexamer formation, probably involved in the storage of insulin. Both the Zn and Mn contents were too low in the guinea-pig islet parenchyma to be reasonably involved in the storage of insulin in the .beta.-granules. Instead, it was suggested that guinea-pig insulin, like hagfish insulin, might crystallize without access to Zn or other heavy metals. Low Zn and Mn contents were also observed in newborn and diabetic guinea-pigs. The islet Zn content was high in the Wistar rat, the Chinese hamster and the spiny mouse. No significant amounts of Mn were found in any of these kinds of islet parenchyma.