Intracellular pH, Na+- and K+-activities at the onset of St. Thomas' cardioplegia: a study with ionselective microelectrodes.

Cellular edema and cardiac arrhythmias are often closely related to intracellular ionic alterations and, moreover, are an actual problem of clinical cardioplegia and ischemia of the heart. In order to investigate whether the clinically widely used cardioplegic solution of the St. Thomas' Hospital may predispose for these complications, membrane potential (EM), intracellular pH (pHi), and intracellular sodium and potassium activity (aiNa- and aiK) in sheep heart Purkinje fibres were directly measured by means of neutral-carrier ion-selective microelectrodes during equilibration of the fibres' extracellular space with the cardioplegic solution.