Decrease in ionic permeability of the cell membrane in guinea‐pig atrial tissue by treatment with antifibrillatory agents and hexobarbitone, determined by means of 86Rb

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Abstract
1 The influence of antifibrillatory agents on the release of previously accumulated 86Rb+ ions was studied in guinea-pig isolated left auricles, incubated in a K+-free Tyrode solution that contained an equivalent concentration (2.7 mm) of Rb+. The auricles were stimulated electrically at a frequency of 100/min and showed entirely “normal” mechanical behaviour in the incubation medium. 2 Quinidine, tetracaine, hexobarbitone-Na and propranolol caused a dose-dependent negative inotropic effect. The frequency of beating (100/min) was usually not affected by these drugs. 3 The reduction in contractile force was accompanied by a dose-dependent inhibition of 86Rb release. The concentration-response curves for both the mechanical effect and the influence on 86Rb release almost coincided for quinidine, although these curves diverged for the other drugs studied. 4 It is suggested that all the four different antifibrillatory drugs cause a general reduction of the membrane permeability to inorganic ions. The mechanism of this membrane stabilization remains unknown.