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CO 2 permeability and carbonic anhydrase activity of rat cardiomyocytes
Author(s) -
AriasHidalgo M.,
AlSamir S.,
Weber N.,
GeersKnörr C.,
Gros G.,
Endeward V.
Publication year - 2017
Publication title -
acta physiologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.591
H-Index - 116
eISSN - 1748-1716
pISSN - 1748-1708
DOI - 10.1111/apha.12887
Subject(s) - sarcolemma , chemistry , carbonic anhydrase , intracellular , biophysics , membrane , biochemistry , biology , enzyme
Aim To determine the CO 2 permeability ( P CO 2 ) of plasma membranes of cardiomyocytes. These cells were chosen because heart possesses the highest rate of O 2 consumption/ CO 2 production in the body. Methods Cardiomyocytes were isolated from rat hearts using the Langendorff technique. Cardiomyocyte suspensions exhibited a vitality of 2–14% and were studied by the previously described mass spectrometric 18 O‐exchange technique deriving P CO 2 . We showed by mass spectrometry and by carbonic anhydrase ( CA ) staining that non‐vital cardiomyocytes are free of CA and thus do not contribute to the mass spectrometric signal, which is determined exclusively by the fully functional vital cardiomyocytes. Results Lysed cardiomyocytes yielded an intracellular CA activity for vital cells of 5070; that is, the rate of CO 2 hydration inside the cell is accelerated 5071‐fold. Using this number, analyses of the mass spectrometric recordings from cardiomyocyte suspensions yield a P CO 2 of 0.10 cm s −1 ( SD ± 0.06, n = 15) at 37 °C. Conclusion In comparison with the P CO 2 of other cells, this value is quite high and about identical to that of the human red cell membrane. As no major protein CO 2 channels such as aquaporins 1 and 4 are present in rat cardiac sarcolemma, the high P CO 2 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 CO 2 of ≥0.1 cm s −1 from this level of cholesterol. We conclude that the low cholesterol establishes a P CO 2 high enough to render the membrane resistance to CO 2 diffusion almost negligible, even under conditions of maximal O 2 consumption of the heart.