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 ca rotid body but also in the wall of the common carotid artery and aroun d each artery arising from the common carotid artery. Effects of chron ic isocapnic hypoxia on the chicken carotid body and the glomus cells in and around the arteries were examined by immunohistochemistry and e lectron microscopy. In chickens exposed to isocapnic hypoxia for 35 da ys, three- to four-fold increase of the carotid body volume was induce d. Immunoreactivity for tyrosine hydroxylase of glomus cells almost co mpletely disappeared. Dense networks of TuJ1-immunoreactive nerve fibe rs were unchanged, whereas peptidergic nerve fibers, i.e., substance P -, calcitonin gene-related peptide-, vasoactive intestinal peptide-, g alanin- and neuropeptide Y-immunoreactive fibers, were decreased in an d around the carotid body. At the electron microscopic level, increase d secretory activity of the glomus cells was verified. Mature dense-co red vesicles were markedly decreased, although prosecretory granules w ere 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 bo dy, 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 immunoreactivi ty for neuropeptide Y, serotonin and chromogranin A. Furthermore, a la rge number of dense-cored vesicles were distributed throughout the cyt oplasm. The glomus cells around each artery arising from the common ca rotid artery were affected by hypoxia, although the degree of their re sponse to hypoxia varied depending on the locations. (C) 1998 Elsevier Science B.V. All rights reserved.