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Carotid body oxygen sensing

¹ Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Sevilla, and ² Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain.

CORRESPONDENCE: J. López-Barneo, Instituto de Biomedicina de Sevilla, Edificio de Laboratorios, Segunda planta, Hospital Universitario Virgen del Rocío, Avenida Manuel Siurot s/n, 41013 Sevilla, Spain. Fax: 34 954617301. E-mail: lbarneo{at}us.es

Keywords: Acute hypoxia, carotid body, chronic hypoxia, ion channels, oxygen sensing, stem cells

Received: April 14, 2008
Accepted April 22, 2008

The carotid body (CB) is a neural crest-derived organ whose major function is to sense changes in arterial oxygen tension to elicit hyperventilation in hypoxia. The CB is composed of clusters of neuron-like glomus, or type-I, cells enveloped by glia-like sustentacular, or type-II, cells. Responsiveness of CB to acute hypoxia relies on the inhibition of O₂-sensitive K⁺ channels in glomus cells, which leads to cell depolarisation, Ca²⁺ entry and release of transmitters that activate afferent nerve fibres. Although this model of O₂ sensing is generally accepted, the molecular mechanisms underlying K⁺ channel modulation by O₂ tension are unknown. Among the putative hypoxia-sensing mechanisms there are: the production of oxygen radicals, either in mitochondria or reduced nicotinamide adenine dinucleotide phosphate oxidases; metabolic mitochondrial inhibition and decrease of intracellular ATP; disruption of the prolylhydroxylase/hypoxia inducible factor pathway; or decrease of carbon monoxide production by haemoxygenase-2. In chronic hypoxia, the CB grows with increasing glomus cell number. The current authors have identified, in the CB, neural stem cells, which can differentiate into glomus cells. Cell fate experiments suggest that the CB progenitors are the glia-like sustentacular cells. The CB appears to be involved in the pathophysiology of several prevalent human diseases.

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