Effects of isoprenaline and phenylephrine on plasma potassium: role of the liver.

A dog liver preparation in situ was used. Intravenous infusion of isoprenaline caused a decrease of plasma potassium levels, which was preceded, in some of the animals infused with higher doses, by a rise in plasma potassium. Propranolol abolished both these effects of isoprenaline, whereas phentolamine was devoided of effects. Liver potassium was not affected by isoprenaline infusions. Phenylephrine caused release of potassium from the liver; this effect was blocked by phentolamine, but not by propranolol. Combination of phenylephrine and isoprenaline induced a super-additive hyperkalemia. Analysis of these results led to the conclusion that the rise in plasma potassium due to phenylephrine might reflect a direct kalemotropic effect and an indirect hypoxemic effect. Isoprenaline seems to increase the hypoxemia caused by phenylephrine by opening the intrahepatic vascular shunts.