Gastrin releasing peptide (GRP) binding sites in human bronchi

The autoradiographic binding site of gastrin releasing peptide (GRP), the 27 amino acid mammalian form of bombesin, were examined in human bronchial mucosa. ¹²⁵I-GRP bound specifically to submucosal glands and the epithelium. There was limited binding to vessels and bronchial smooth muscle. These observations suggest that GRP or GRP immunoreactive peptides which are present in nerve fibres and pulmonary neuroendocrine cells, may act upon glandular GRP receptors to induce mucus secretion, but that GRP would probably have little effect on vascular permeability or tracheobronchial smooth muscle tone.