The location of VIP in the pancreas of man and rat

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Abstract
VIP has powerful stimulatory effects on both endocrine and exocrine pancreas but its localisation within the gland has not been established. In this study, human pancreas was obtained fresh at surgery (eleven) or within four hours of death (seven). The pancreas was also removed from rats (twenty-two). Immunocytochemical staining showed VIP to be present in fine nerve fibres in all areas of the pancreas. Many fibres were seen in the exocrine pancreas, running between the acini, and around ducts and blood vessels. In addition, dense networks of fibres were observed forming meshes around islets and occasional ganglia were found containing immunoreactive cell bodies. In general, there were fewer VIP fibres in the rat pancreas than in the human, but overall distribution was identical. The mean VIP content of whole human pancreatic tissue was 42±10 pmol/g wet weight (38±9 pmol/g in head, 49±6 pmol/g in body and 42±11 pmol/g in tail). Whole rat pancreatic tissue contained 28±7 pmol/g wet weight while preparations of isolated islets were found to contain 374±30 pmol/g. It is possible that the heavy VIP innervation of the islets described here indicates a role in the regulation of islet hormone release.