Immunohistochemical Study of the Carotid Body During Acute Hypoxia
The carotid body is known to function as a chemoreceptor that is sensitive to inadequate oxygenation (hypoxia), hypercapnia and increased acidity in the arterial blood supply. Its regulatory effect is considered to be dependent on the ratio of oxygen to carbon dioxide. Differences in the plasma concentrations of these gases are measured by peripheral and central chemoreceptors located in the carotid body and brainstem, respectively. The carotid body consists basically of a parenchymal mass of clusters and strands of granular chromaffin type I glomus cells surrounded by nongranular type II glomus cells, with sinusoidal capillaries in close contact with both cell types. Afferent nerve fibers from the sinus branch of the glossopharyngeal nerve and postganglionic fibers of the sympathetic cervical ganglia form a dense network in contact with the type 1 cells. Some free nerve endings are present in the pericapillary space. Excitatory impulses generated in these fibers suspected to be true chemoreceptor nerve endings - are transmitted to the vasomotor center of the medulla oblongata. The glomus cells, classed as AUDP cells, are polygonal with light, round nuclei, abundant mitochondria and free ribosomes, a well developed ergastoplasm, and a Golgi apparatus. The expression of SP-22 protein is reported to be enhanced about 1.5- to 4.6-fold when bovine aortic endothelial cells (BAEC) are exposed to various types of oxidative stress, including mitochondrial respiratory inhibitors which increase the generation of superoxide in the mitochondria. BAEC with an increased level of the mitochondrial protein SP-22 resulting from mild oxidative stress become tolerant to subsequent intense oxidative stress. SP-22 is reported to be a member of the thioredoxin-dependent peroxidase family, suggesting that it may be one of the components of the antioxidant system in mitochondria, which are the major sites where reactive oxygen intermediates are generated (Araki etal. 1999)
KeywordsCarotid Body Acute Hypoxia Bovine Aortic Endothelial Cell Glomus Cell Free Nerve Ending
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