Calcitonin and calcitonin gene-related peptide immunoreactivity and colocalization in newborn cat lung.

Calcitonin (CT) and calcitonin gene-related peptide (CGRP) are generated by alternate RNA processing from alpha and beta CT/CGRP genes. In this report, an immunocytochemical investigation was undertaken on the occurrence and distribution of immunoreactive CT as well as its colocalization with CGRP in newborn cat bronchopulmonary endocrine cells. A widespread distribution of solitary endocrine cells and neuroepithelial bodies immunostained for CT was recorded within the lung. In all animals studied, CT immunoreactivity represents a subpopulation of CGRP positive cells, while the intrapulmonary nerve fibers contain only CGRP. To the best of our knowledge, this is the first time that CT and its colocalization with CGRP have been demonstrated immunocytochemically in the cat lung. Our results indicate, that different molecular processing of both CT/CGRP genes may be represented by different patterns in the cellular immunoreactivity of the synthetized peptides.