Immunocytochemical identification of islet cells containing calcitonin gene-related peptide-like immunoreactivity in the plains rat pancreas (Pseudomys australis)
Edwin, N.; Leigh, C.M.
Singapore Medical Journal 40(8): 528-530
1999
ISSN/ISBN: 0037-5675 PMID: 10572493 Document Number: 502536
Background/Aim: Calcitonin gene-related peptide (CGRP) is a product of alternative RNA processing of the calcitonin gene. Its dual occurrence in nerves and endocrine cells makes it likely to be both a neuropeptide and an endocrine (paracrine) messenger. The purpose of this study was to determine whether CGRP-containing cells are present in the pancreas of the plains rat (Pseudomys australis). Methods: Paraffin embedded tissue from four adult plains rats was sectioned and stained using an immunocytochemical avidin-biotin-peroxidase (ABC) method. The sections were incubated with rabbit polyclonal rat CGRP (Peninsula Labs, Belmont, CA) diluted 1:1000, in a solution consisting of 1% bovine serum albumin and 0.05% sodium azide in 0.1 mol/L of PBST overnight in a humid chamber at room temperature. Immunolocalisation was shown in the islets of Langerhans tissue. A negative control using normal serum was used to test the specificity of the individual immunoreaction and on all occasions therewas no immunostaining. Results: For the purpose of colocalisation of CGRP immunoreactive cells, mirror images of stained sections were stained for CGRP and insulin, somatostatin, glucagon and pancreatic polypeptide. The immunostained cells of the same islet were assessed for colocalisation and found to be identical with insulin cells. Conclusion: The dual localisation of CGRP immunoreactivity in neuronal and endocrine elements provide further evidence for both a neurocrine and hormonal role for CGRP in endocrine and exocrine functions. In the plains rats, we have shown CGRP to be an endocrine peptide.