CO₂permeability and carbonic anhydrase activity of rat cardiomyocytes

Abstract

In comparison with the P_CO₂ of other cells, this value is quite high and about identical to that of the human red cell membrane. As no major protein CO₂ channels such as aquaporins 1 and 4 are present in rat cardiac sarcolemma, the high P_CO₂ of this membrane is likely due to its low cholesterol content of about 0.2 (mol cholesterol)·(mol total membrane lipids)^-1 . Previous work predicted a P_CO₂ of ≥0.1 cm s^-1 from this level of cholesterol. We conclude that the low cholesterol establishes a P_CO₂ high enough to render the membrane resistance to CO₂ diffusion almost negligible, even under conditions of maximal O₂ consumption of the heart.