Effect of acute hypoxia on glomus cell Em and m as measured by fluorescence imaging

Roy, Arijit, Jinqing Li, Abu-Bakr Al-Mehdi, Anil Mokashi, and Sukhamay Lahiri. Effect of acute hypoxia on glomus cell Em and m as measured by fluorescence imaging. J Appl Physiol 93: 1987–1998, 2002. First published August 2, 2002; 10.1152/japplphysiol.00725.2001.—We have reinvestigated the hypothesis of the relative importance of glomus cell plasma and mitochondrial membrane potentials (Em and 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 Em 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 Em to acute hypoxia ( 10 Torr PO2) 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 Em hyperpolarization was confirmed with high CO ( 500 Torr). Glomus cell m depolarization was indirectly assessed by a decrease in JC-1 (a cationic probe) fluorescence. Accordingly, 1 M carbonyl cyanide p-trifluoromethoxyphenylhydrazone (an uncoupler of oxidative phosphorylation), high CO (a metabolic inhibitor), and acute hypoxia ( 10 Torr PO2) 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.