Different effects of prolonged isocapnic hypoxia on the carotid body and the glomus cells in the wall of the common carotid artery of the chicken.

In the chicken, glomus cells are widely distributed not only in the carotid body but also in the wall of the common carotid artery and around each artery arising from the common carotid artery. Effects of chronic isocapnic hypoxia on the chicken carotid body and the glomus cells in and around the arteries were examined by immunohistochemistry and electron microscopy. In chickens exposed to isocapnic hypoxia for 35 days, three- to four-fold increase of the carotid body volume was induced. Immunoreactivity for tyrosine hydroxylase of glomus cells almost completely disappeared. Dense networks of TuJ1-immunoreactive nerve fibers were unchanged, whereas peptidergic nerve fibers, i.e., substance P-, calcitonin gene-related peptide-, vasoactive intestinal peptide-, galanin- and neuropeptide Y-immunoreactive fibers, were decreased in and around the carotid body. At the electron microscopic level, increased secretory activity of the glomus cells was verified. Mature dense-cored vesicles were markedly decreased, although prosecretory granules were numerous around Golgi complexes. Many immature glomus cells filled with rough endoplasmic reticulum and free ribosomes, also appeared in the carotid bodies of hypoxic chickens. In contrast to the carotid body, the glomus cells located in the wall of the common carotid artery revealed no changes after long-term hypoxia. The cells in the hypoxic chickens, as well as normal controls, expressed intense immunoreactivity for neuropeptide Y, serotonin and chromogranin A. Furthermore, a large number of dense-cored vesicles were distributed throughout the cytoplasm. The glomus cells around each artery arising from the common carotid artery were affected by hypoxia, although the degree of their response to hypoxia varied depending on the locations.