Cellular Cl concentration in the rat left ventricle was 8.2 +/- 0.5 mmol/kg cell water, corresponding to an equilibrium potential of -70 to -80 mV, with a very fast Cl exchange flux.
The study demonstrates that cellular chloride concentration in the rat ventricle is lower than previously estimated and that chloride exchange flux is exceptionally fast for myocardial ion transport.
The cellular Cl content and concentration (Clcell) and the cellular uptake of 36Cl have been measured in the rat left ventricle in vivo. The in vitro efflux of 36Cl from perfused contracting ventricles preequilibrated with 36Cl in vivo was also determined at 22, 30, and 38 degrees C. Clcell was 8.2 +/- 0.5 mmol/kg cell water, corresponding to a calculated equilibrium potential of Cl of -70 to -80 mV. This figure for Clcell is significantly lower than previous estimates in the literature, which were subject to an analytical error leading to overestimation of muscle Cl content obtained coulometrically. At 38 degrees C, Cl exchange under quasi-steady-state conditions was 31.2 mumol . (g dry ventricle . min)-1 or 42.5 pmol . (cm2 plasma membrane . s).-1 Apparent activation energy of the flux was 10.4 kcal/mol. At 22 degrees C, no dependence of the exchange on contraction frequency was detectable over a range of 80-160 contractions/min. The Cl exchange flux is among the fastest, if not the fastest. known for myocardial ion transport.
Polimeni et al. (Thu,) reported a other. Measurement of cellular Cl content and 36Cl uptake/efflux was evaluated on Cellular Cl content and concentration ([Cl]cell). Cellular Cl concentration in the rat left ventricle was 8.2 +/- 0.5 mmol/kg cell water, corresponding to an equilibrium potential of -70 to -80 mV, with a very fast Cl exchange flux.