Pulmonary neuroendocrine cells in species at high altitude

Ever since pulmonary neuroendocrine cells were first described, a chemoreceptor function has been attributed to them. This hypothesis proposes that the innervated clusters of these cells, which are known to degranulate when the oxygen tension around them is reduced, respond to hypoxia to initiate activity in a reflex arc and ultimately adjust some aspect of pulmonary function. If this were true, one might expect to see changes in the pulmonary neuroendocrine system in species exposed to the unremitting hypoxia at natural high altitude. Whilst evidence from some studies suggests that such changes do occur, others have been unable to demonstrate any effect. To some extent this may be attributable to species variability, but might also reflect whether the organism is genetically adapted or merely acclimatized to life in an oxygen-poor environment.