Weibel-Palade bodies as a storage site of calcitonin gene-related peptide and endothelin-1 in blood vessels of the rat carotid body

Background: The vasculature of the carotid body has been considered to play a role in the regulation of blood flow into this organ. This light and electron microscope immunocytochemistry deals with endothelium-dependent vasomotion by vasodilatory calcitonin gene-related peptide (CGRP) and vasoconstrictive endothelin-1 (ET-1). Methods: After adult male rats were perfused with a solution of periodate-lysine-paraformaldehyde through the left ventricle, the carotid artery bifurcations were isolated and utilized for light and electron microscope immunolabelings with CGRP and ET-1 primary antisera. Results: By light microscope immunocytochemistry, immunoreactions to CGRP were seen along the endothelium of the carotid body artery (CBA) and its branches, and those of ET-1 were observed along the endothelium of the intralobular capillaries in addition to the above vessels. By immunoelectron microscopy, immunoreactive gold particles of CGRP and ET-1 were identified in the rough endoplasmic reticulum (rER) and in the Weibel-Palade (WP) bodies of endothelial cells of the CBA and its branches. Colocalization of both immunoreactive gold particles was observed in the same WP body. Immunoreactive gold particles of CGRP were also identified in the rER, Golgi apparatus, and specific granules of the dark, glomus cells. Conclusions: Conceivably, CGRP and ET-1 are synthesized in the rER of these endothelial cells and are stored in the WP bodies for the autoregulation of blood flow. (C) 1997 Wiley-Liss, Inc.