The Human Carotid Body and its Role in Ventilatory Acclimatization to Hypoxia

Abstract

The carotid body (CB) is a paired neural crest-derived small ovoid mass of tissue that registers the changes in the arterial blood levels of oxygen, carbon dioxide as well as hydrogen ion concentration and reacts to these changes by the initiation of an appropriate respiratory and cardiovascular response. The human CB shows remarkable structural plasticity and this plasticity underlies the so-called ventilatory acclimatization to hypoxia. The CB morphological changes to high-altitude adaptation include glomus cell hypertrophy and hyperplasia, marked vasodilation and vascular remodeling. The hypoxic CB also shows extraordinary plasticity in different neurotransmitter systems. The altered neurochemical profile of the chemosensory cells comprises elevated catecholamine contents, changes in purinergic mechanisms, up-regulation of nitric oxide metabolism, a marked reduction in peptide levels and production of neurotrophic factors. The structural changes and complex interactions among transmitters markedly influence hypoxia-induced responses in the human CB, thus implying its essential role in ventilatory acclimatization.