Chronic hypoxia in vitro increases volume of dissociated carotid body chemoreceptors

Exposure of humans or animals to chronic hypoxia results in enlargement of the carotid body, a respiratory organ that controls ventilation. The underlying mechanisms are unclear but involve hypertrophy of the chemoreceptor glomus cells. To test whether the latter response can occur independent of the circulation or neural inputs, we exposed cultures of dissociated rat carotid body to chronic hypoxia (2-3 weeks in 6% O2), and compared the 3-D cell volume of immunofluorescent, tyrosine hydroxylase positive (TH+) glomus cells, from data sets obtained by serial confocal microscopy. We found a dramatic increase in volume (3-4 x control) of hypoxia-treated TH + cells, suggesting that glomus cell hypertrophy during chronic hypoxia in vivo is likely due to a local effect of low PO2, rather than the production of ectopic growth factors.