Effect of acute hypoxia on glomus cell Em and psi m as measured by fluorescence imaging.
We have reinvestigated the hypothesis of the relative importance of glomus cell plasma and mitochondrial membrane potentials (E(m) and psi(m), respectively) in acute hypoxia by a noninvasive fluorescence microimaging technique using the voltage-sensitive dyes bis-oxonol and JC-1, respectively. Short-term (24 h)-cultured rat glomus cells and cultured PC-12 cells were used for the study. Glomus cell E(m) depolarization was indirectly confirmed by an increase in bis-oxonol (an anionic probe) fluorescence due to a graded increase in extracellular K(+). Fluorescence responses of glomus cell E(m) to acute hypoxia (approximately 10 Torr Po(2)) indicated depolarization in 20%, no response in 45%, and hyperpolarization in 35% of the cells tested, whereas all PC-12 cells consistently depolarized in response to hypoxia. Furthermore, glomus cell E(m) hyperpolarization was confirmed with high CO (approximately 500 Torr). Glomus cell psi(m) depolarization was indirectly assessed by a decrease in JC-1 (a cationic probe) fluorescence. Accordingly, 1 microM carbonyl cyanide p-trifluoromethoxyphenylhydrazone (an uncoupler of oxidative phosphorylation), high CO (a metabolic inhibitor), and acute hypoxia (approximately 10 Torr Po(2)) consistently depolarized the mitochondria in all glomus cells tested. Likewise, all PC-12 cell mitochondria depolarized in response to FCCP and hypoxia. Thus, although bis-oxonol could not show glomus cell depolarization consistently, JC-1 monitored glomus cell mitochondrial depolarization as an inevitable phenomenon in hypoxia. Overall, these responses supported our "metabomembrane hypothesis" of chemoreception.
Roy
Arijit
A
Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6085, USA.
Li
Jinqing
J
Al-Mehdi
Abu-Bakr
AB
Mokashi
Anil
A
Lahiri
Sukhamay
S
D000208:Acute Disease; D000818:Animals; D001562:Benzimidazoles; D002232:Carbocyanines; D002248:Carbon Monoxide / Q000494:pharmacology; D002344:Carotid Body / Q000166:cytology / Q000502:physiology*; D005456:Fluorescent Dyes; D000860:Hypoxia / Q000503:physiopathology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008856:Microscopy, Fluorescence / Q000379:methods*; D008928:Mitochondria / Q000502:physiology; D010100:Oxygen / Q000494:pharmacology; D016716:PC12 Cells; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013858:Thiobarbiturates
D001562:Benzimidazoles; D002232:Carbocyanines; D005456:Fluorescent Dyes; D013858:Thiobarbiturates; C068624:5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolocarbocyanine; C025284:bis(1,3-diethylthiobarbiturate)trimethineoxonol; D002248:Carbon Monoxide; D011188:Potassium; D010100:Oxygen