Regulatory peptides and the lung

Abstract

Powerful regulatory peptides have been found in nerves and cells of peripheral tissues. The lung has been found to contain almost all the active peptides previously described. The respiratory tracts of three mammalian species--rat, guinea pig, and cat--were examined, and significant quantities of vasoactive intestinal peptide (VIP), bombesin, substance P, somatostatin, and cholecystokinin were found. The VIP nerves were most numerous in the upper respiratory tract, particularly the nasal mucosa. A close association with seromucous glands, blood vessels, and bronchial smooth muscle was particularly noteworthy and paralleled the pharmacologic actions of VIP, i.e., secretomotor, vasodilatory, and smooth muscle relaxation. In contrast, bombesin was localized to epithelial amine precursor uptake and decarboxylation (APUD) cells, which were particularly numerous in the fetus, suggesting a possible role in control of pulmonary growth. Substance P, a peptide thought to subserve a sensory role, was localized to fine nerve fibers, with a particularly close association with bronchial epithelium. The quantities of somatostatin and cholecystokinin were very low and, therefore, difficult to localize. In the human, bombesin and VIP were present in considerable quantities. Bombesin cells were again most numerous in the fetal and neonatal small bronchi and bronchiolar epithelium. During development VIP-ergic nerves showed little change in number but demonstrated a gradient of distribution, with the largest quantities located in the extrapulmonary airways. In preliminary investigations of pulmonary disease, bombesin levels were found to be very greatly reduced with acute hyaline membrane disease in the newborn.(ABSTRACT TRUNCATED AT 250 WORDS)