Detection of hypoxia-evoked ATP release from chemoreceptor cells of the rat carotid body.
The carotid body (CB) is a chemosensory organ that detects changes in chemical composition of arterial blood and maintains homeostasis via reflex control of ventilation. Thus, in response to a fall in arterial PO(2) (hypoxia), CB chemoreceptors (type I cells) depolarize, and release neurotransmitters onto afferent sensory nerve endings. Recent studies implicate ATP as a key excitatory neurotransmitter released during CB chemoexcitation, but direct evidence is lacking. Here we use the luciferin-luciferase bioluminescence assay to detect ATP, released from rat chemoreceptors in CB cultures, fresh tissue slices, and whole CB. Hypoxia evoked an increase in extracellular ATP, that was inhibited by L-type Ca(2+)channel blockers and reduced by the nucleoside hydrolase, apyrase. Additionally, iberiotoxin (IbTX; 100 nM), a blocker of O(2)-sensitive Ca(2+)-dependent K(+) (BK) channels, stimulated ATP release and largely occluded the effect of hypoxia. These data strongly support a neurotransmitter role for ATP in carotid body function.
Department of Biology, McMaster University, Hamilton, Ont., Canada L8S 4K1.
Josef
J
Buttigieg
Colin A
CA
Nurse
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000502:physiology*; D002344:Carotid Body / Q000378:metabolism*; D015687:Cell Hypoxia / Q000502:physiology*; D002478:Cells, Cultured; D002628:Chemoreceptor Cells / Q000378:metabolism; D046508:Culture Techniques; D051381:Rats; D017208:Rats, Wistar; D013050:Spectrometry, Fluorescence / Q000379:methods*
D020746:Calcium Channels, L-Type; D000255:Adenosine Triphosphate; D002118:Calcium