Release of 5-hydroxytryptamine by hypoxia from epithelioid cells of chicken thoracic aorta.

Epithelioid cells in the chicken thoracic aorta are shown to contain 5-hydroxytryptamine (5-HT) in immunocytochemical studies. To determine whether these cells act as chemoreceptors, as do type I cells of the carotid body, we examined the effects of hypoxia and acidosis on the release of 5-HT from the chicken thoracic aorta. Hypoxia caused the output of 5-HT in incubation medium. A reduction of pH to 6.8 failed to evoke 5-HT release. The response to hypoxia was inhibited by the removal of extracellular Ca2+ and by nifedipine and omega-conotoxin GVIA. These results suggest that epithelioid cells in the chicken thoracic aorta are chemoreceptors which sense a decrease in PO2 and then release 5-HT by Ca2+ influx through voltage-dependent L- and N-type Ca2+ channels. The epithelioid cells in the chicken aorta may be a useful model for pharmacological and physiological studies of 5-HT-containing cells.