Simultaneous immunohistochemical localization of gastrin releasing peptide (GRP) and calcitonin (CT) in human bronchial endocrine-type cells.

Formalin-fixed paraffin-embedded sections of fetal and adult human lungs were examined for the localization of gastrin releasing peptide (GRP) and calcitonin (CT) in bronchial endocrine-type cells with the indirect immunoperoxidase method. In fetal lungs, the appearance of CT was much later than that of GRP, and CT-containing cells were less frequent than GRP-containing cells which, in later fetal life, formed "neuroepithelial bodies (NEB)". NEB revealed little CT immunoreactivity. The serial section technique demonstrated that all CT immunoreactants in fetal and neonatal lungs were present within GRP-containing cells. An increase of CT immunoreactivity in GRP-containing cells was observed in perinatal lungs. The lung of a neonate who died of hyaline membrane disease contained the most abundant CT immunoreactants. In adult lungs, CT immunoreactivity was identified in some GRP-containing cells but cells containing only GRP or CT were also present. Cells containing both hormones occasionally formed hyperplastic foci in the bronchi of fibrotic lungs. Most cells of pulmonary tumorlets consistently showed GRP immunoreactivity, but the number of CT immunoreactive cells in them varied greatly.