COLOCALIZATION OF PEPTIDE-HORMONES IN NEUROENDOCRINE CELLS OF HUMAN FETAL AND NEWBORN LUNGS - AN ELECTRON-MICROSCOPIC STUDY

This study investigated the colocalization of the peptide hormones bom besin or calcitonin with calcitonin gene related peptide (CGRP) in neu roendocrine cells (NE) in the lungs of human fetuses of varying gestat ional ages and in the lungs of newborn infants who died with acute or chronic lung disease in the first weeks or months after birth. Double immunolabeling of dense core granules for these peptides was also stud ied in this same patient population. On-grid double gold immunolabelin g was carried out on 29 subjects using anti-bombesin and anti-CGRP and on 22 subjects using anti-calcitonin and anti-CGRP as primary antibod ies, the secondary antibodies being labeled with different-size gold s pheres. Colocalization of both bombesin and calcitonin with CGRP was d emonstrated, not only in the same NE cell, but also on the same dense core granule. Colocalization was rarely found in normal fetuses, and m ost frequently found in newborn infants with acute lung disease, usual ly hyaline membrane disease (HMD), or with the development of chronic lung disease in the first weeks or months after birth. Double labeling of the same dense core granules might imply action of peptides in con cert, or perhaps one peptide acting in a paracrine role (e.g., on bron chial or bronchiolar smooth muscle) and the second peptide acting in a n autocrine fashion on the parent cell (e.g., in the regulation of gra nule production or release).