Decreasing the pH of the bathing medium from 7.5 to 6.1 in isolated rabbit atrial muscle increased extracellular K+ activity from a control level of 3.6 mM to 4.9 mM.
Absolute Event Rate: 4.9% vs 3.6%
The extracellular and intracellular potassium (K+) activities of isolated superfused rabbit atrial muscle were measured using K+-sensitive liquid ion exchanger microelectrodes. When the pH of the bathing medium was decreased from 7.5 to 6.8, intracellular K+ activity fell and extracellular K+ activity rose from a mean control level of 3.6 mM to a new steady state level of 3.9 mM after 1 hour. When the pH was further decreased to 6.1, extracellular K+ activity increased to a mean of 4.9 mM. Following the change in pH, the increase in extracellular K+ activity occurred over a period of 30-40 minutes at which time a stable value was reached and maintained for the next hour. On return to normal pH the extracellular K+ activity returned to control with a time constant of 20 minutes or less. Measurements of intracellular K+ activity over 1 hour showed a mean loss of 3 mM at pH 6.8 and a mean loss of 8 mM at pH 6.1. The loss was reversible within 20 minutes of return to control pH. The increase in extracellular K+ activity was accompanied by a decrease in resting membrane potential as well as decreases in maximum dv/dt and overshoot of the action potential. The action potential contour underwent complex changes consisting of decrease in the plateau and a prolongation of the time to full repolarization.
Skinner et al. (Mon,) conducted a other in Isolated superfused rabbit atrial muscle. Decreased pH vs. Normal pH (7.5) was evaluated on Extracellular potassium (K+) activity. Decreasing the pH of the bathing medium from 7.5 to 6.1 in isolated rabbit atrial muscle increased extracellular K+ activity from a control level of 3.6 mM to 4.9 mM.