Interactive effects of K+, acidosis, and catecholamines on isolated rabbit heart: implications for exercise

effects of K+, acidosis, and catecholamines on isolated rabbit heart: implications for exercise. J. Appl. Physiol. 77(3): 1164-1171, 1994.-Intense exercise can double arterial K+ concen-tration, decrease pH by 0.4 units, and increase catecholamines &fold. Any one of these changes may be cardiotoxic in a sub-ject at rest, yet these changes are well tolerated in exercise. We tested the interactive effects of extracellular K+ concentration ([K’],), metabolic acidosis (pH 7.0), and raised catecholamines in the isolated working rabbit heart when they were changed with similar kinetics and concentrations to those seen in exer-cise. Raised [K+], (8 and 12 mM) significantly decreased aortic flow (AF) by 23 and 76%, respectively (P < 0.01). Acidosis de-creased AF by 19 % (P < 0.05) and by 38 % in combination with 8 mM [K’], (P < 0.05), making their combined effect additive. Either epinephrine (80 nM), norepinephrine (80 nM) or extra