The meaning of H2O2 generation in carotid body cells for PO2 chemoreception.
The rat carotid body is able to generate H2O2 in type-I cells with the aid of an electron-transferring chain with cytochrome b as the major component as it can be detected by spectrophotometry as well as confocal laser-microscopy. This cytochrome b is reducible by hypoxia, but not by cyanide, indicating that it does not participate in the energy production by the respiratory chain. The carotid body possesses a glutathione peroxidase (GPO) which scavenges H2O2 and other organic hydroperoxides. The nervous chemoreceptor discharge can be inhibited by external application of hydroperoxides with a similar half maximal value (60-80 microM) as used to stimulate GPO. A hypothetical signal chain is described which suggests the involvement of cytochrome b as an O2 sensor in PO2 chemoreception of the carotid body and the degradation of H2O2 by glutathione to control the K(+)-conductivity of carotid body cells.
Acker
H
H
Max-Planck-Institut für Sytemphysiologie, Dortmund, FRG.
Bölling
B
B
Delpiano
M A
MA
Dufau
E
E
Görlach
A
A
Holtermann
G
G
D000818:Animals; D002344:Carotid Body / Q000166:cytology / Q000378:metabolism*; D002628:Chemoreceptor Cells / Q000378:metabolism*; D046508:Culture Techniques; D003573:Cytochrome b Group / Q000378:metabolism; D005609:Free Radicals / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism*; D010545:Peroxides / Q000378:metabolism*; D010783:Photometry; D051381:Rats; D013552:Swine
D003573:Cytochrome b Group; D005609:Free Radicals; D010545:Peroxides; D006861:Hydrogen Peroxide; D005979:Glutathione Peroxidase