Chapter 18 - O2 and CO2 Detection by the Carotid and Aortic Bodies

Abstract

The carotid and aortic bodies are the sensory organs for monitoring arterial blood oxygen (O2) and carbon dioxide (CO2) levels. The type I cells, which are of neuronal phenotype, are the primary site of sensory transduction in the carotid and aortic bodies. Although the carotid bodies sense the reduction in partial pressure of O2, the aortic bodies are more sensitive to changes in arterial blood O2 content. Emerging evidence suggests that complex interplay among three gases—oxygen, carbon monoxide, and hydrogen sulfide—and their interaction with K+ channels and/or mitochondrial electron transport chain in type I cells is necessary for carotid body sensory nerve excitation by hypoxia. CO2 sensing by the carotid body requires changes in intracellular pH in type I cells. Available evidence, albeit limited, suggests that transduction processes similar to those identified in the carotid body also contribute to O2 and CO2 sensing by the aortic body.