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The effect of acidosis on systolic Ca 2+ and sarcoplasmic reticulum calcium content in isolated rat ventricular myocytes
Author(s) -
Choi H. S.,
Trafford A. W.,
Orchard C. H.,
Eisner D. A.
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.00661.x
Subject(s) - calcium , acidosis , endoplasmic reticulum , myocyte , chemistry , medicine , intracellular , bicarbonate , butyrate , endocrinology , biophysics , biochemistry , biology , fermentation
1 We have investigated the mechanisms responsible for the changes of systolic Ca 2+ that occur in voltage‐clamped rat ventricular myocytes during acidosis produced by application of the weak acid butyrate (30 mM). Intracellular pH regulation was inhibited with dimethylamiloride (bicarbonate‐free solution). 2 The application of butyrate produced an intracellular acidification of 0.33 pH units. This was accompanied by a decrease in systolic Ca 2+ to about 50 % of control. However, within 2 min, systolic Ca 2+ returned to control levels. 3 The decrease in systolic Ca 2+ was accompanied by a decrease in the Na + ‐Ca 2+ exchange current observed on repolarisation so that the calculated Ca 2+ efflux on Na + ‐Ca 2+ exchange was less than the entry on the L‐type Ca 2+ current. The magnitude of the Na + ‐Ca 2+ exchange current recovered along with systolic Ca 2+ until it equalled the Ca 2+ entry on the L‐type Ca 2+ current. 4 From the measurement of Ca 2+ fluxes, it was calculated that, during acidosis, the cell gains 121.6 ± 16.2 μmol l −1 of Ca 2+ . This is equal to the measured increase of sarcoplasmic reticulum (SR) calcium content obtained by applying caffeine (20 mM) and integrating the resulting Na + ‐Ca 2+ exchange current. 5 We conclude that the recovery of the amplitude of the systolic Ca 2+ transient is due to decreased SR calcium release, resulting in reduced Ca 2+ efflux from the cell leading to increased SR calcium content.