Hyperbaric oxygenation alters carotid body ultrastructure and function.
We previously demonstrated that chronic normobaric hyperoxia (NH) for 60-67 h attenuated the carotid chemosensory response to hypoxia, probably initiated by the generation of reactive oxygen species (ROS). Since biological systems are affected by oxygen in a dose-dependent manner, we hypothesized that hyperbaric oxygenation (HBO) would affect the cellular mechanisms of oxygen chemoreception in a shorter time. To test the hypothesis, we studied the effects of oxygen at 5 atmospheres absolute (ATA) on cats (n = 7) carotid body ultrastructure and chemosensory responses to hypoxia, hypercapnia, and to bolus injections of cyanide, nicotine and dopamine. Four control cats breathed room air at 1 ATA. At the termination of the experiments, carotid bodies from 4 cats in each group were fixed and prepared for electron microscopy and morphometry. On the average, HBO diminished the chemosensory responsiveness to hypoxia (P < 0.01, unpaired t-test) within about 2 h, supporting the hypothesis. The responses to hypercapnia or bolus injections of cyanide, nicotine and dopamine were normal. HBO did not diminish the distribution of the dense-cored vesicles but significantly increased the mean volume-density of mitochondria and decreased the cristated area per mitochondrion in the glomus cells. The latter suggests a link between oxidative metabolism and chemosensing, and the former excludes availability of neurotransmitters being the cause of the blunted chemosensory response to hypoxia.
Torbati
D
D
Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia.
Sherpa
A K
AK
Lahiri
S
S
Mokashi
A
A
Albertine
K H
KH
DiGiulio
C
C
D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism; D002344:Carotid Body / Q000378:metabolism* / Q000648:ultrastructure; D002415:Cats; D002628:Chemoreceptor Cells / Q000378:metabolism; D003486:Cyanides / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology; D006931:Hyperbaric Oxygenation; D008854:Microscopy, Electron; D009538:Nicotine / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism
D003486:Cyanides; D002245:Carbon Dioxide; D009538:Nicotine; D010100:Oxygen; D004298:Dopamine