Calcitonin gene-related peptide immunoreactivity in adult mouse lung

Calcitonin gene-related peptide (CGRP) is a 37 amino acid peptide coded by the calcitonin gene that is produced by thyroid C cells and medullary carcinoma. It is also widely distributed in neurons and endocrine cells throughout the body. The presence of CGRP in the lungs suggests that this peptide exerts important regulatory actions at this level, and it can act like a neuroregulator released both from nerve terminals and neuroendocrine (NE) cells. To understand the role of CGRP in the lung, it is important to explore its localization in different species. In this paper, we analyse the presence and localization of CGRP in the adult mouse lung using an immunocytochemical staining method. Our results show a widespread distribution of this peptide in isolated neuroendocrine cells and neuroepithelial bodies (NEBs), as well as in nerve fibres distributed in many areas of the lung, including bronchi and bronchioli. These fibres are in close contact with epithelium, neuroendocrine cells and smooth muscle. In addition, some immunostained nerve cell bodies and immunoreactive intrinsic ganglion cells can be shown. CGRP has been previously demonstrated in the mammalian lung using immunocytochemistry. To the best of our knowledge, this is the first time that CGRP has been immunocytochemically demonstrated in the mouse lung both in NE cells, NEBS, ganglion cells and in nerve fibres which are related to neuroendocrine cells.