Effects of CO₂, Bicarbonate and pH on the Performance of Isolated Perfused Guinea Pig Hearts

Guinea pig hearts were perfused with a balanced ion solution in which the pH was altered either by changing the CO 2 tension of the gas in equilibrium with the solution or by varying the bicarbonate concentration of the solution. Heart rates, contraction amplitudes, and coronary flow rates were affected by changes in pCO 2 or HCO 3 – concentration of the perfusing solution only when a change in pH resulted. Increasing the acidity produced a decrease in heart rate and contraction amplitude and an increase in coronary flow. High levels of bicarbonate (50 mm/l.) were sometimes slightly depressant to the heart even when pH was held constant.