title: CO2 and HCO3- Permeability of the Rat Liver Mitochondrial Membrane.
abstract: OBJECTIVE
  Across the mitochondrial membrane an exceptionally intense exchange of O2 and CO2 occurs. We have asked, 1) whether the CO2 permeability, PM,CO2, of this membrane is also exceptionally high, and 2) whether the mitochondrial membrane is sufficiently permeable to HCO3- to make passage of this ion an alternative pathway for exit of metabolically produced CO2.
  
  
  METHODS
  The two permeabilities were measured using the previously published mass spectrometric 18O exchange technique to study suspensions of mitochondria freshly isolated from rat livers. The mitochondria were functionally and morphologically in excellent condition.
  
  
  RESULTS
  The intramitochondrial CA activity was exclusively localized in the matrix. PM,CO2 of the inner mitochondrial membrane was 0.33 (SD ± 0.03) cm/s, which is the highest value reported for any biological membrane, even two times higher than PM,CO2 of the red cell membrane. PM,HCO3- was 2· 10-6 (SD ± 2· 10-6) cm/s and thus extremely low, almost 3 orders of magnitude lower than PM,HCO3- of the red cell membrane.
  
  
  CONCLUSIONS
  The inner mitochondrial membrane is almost impermeable to HCO3- but extremely permeable to CO2. Since gas channels are absent, this membrane constitutes a unique example of a membrane of very high gas permeability due to its extremely low content of cholesterol.
authors: Abt. Molekular- und Zellphysiologie, AG Vegetative Physiologie 4220, Medizinische Hochschule Hannover, Hannover, Italy.
authors: Mariela
authors: M
authors: Arias-Hidalgo
authors: Jan
authors: J
authors: Hegermann
authors: Georgios
authors: G
authors: Tsiavaliaris
authors: Fabrizio
authors: F
authors: Carta
authors: Claudiu T
authors: CT
authors: Supuran
authors: Gerolf
authors: G
authors: Gros
authors: Volker
authors: V
authors: Endeward
mesh_terms: D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D001692:Biological Transport; D002245:Carbon Dioxide / Q000378:metabolism*; D007700:Kinetics; D008099:Liver; D008297:Male; D013058:Mass Spectrometry; D008930:Mitochondria, Liver / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000737:chemistry / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010103:Oxygen Isotopes; D010539:Permeability; D051381:Rats; D011917:Rats, Inbred Lew
chemical_list: D001639:Bicarbonates; D010103:Oxygen Isotopes; D002245:Carbon Dioxide; D010100:Oxygen