Factors Affecting the Action of Lanatoside C on the Potassium Content of Isolated Perfused Guinea Pig Hearts

Abstract

Concns. of lanatoside C (10-6-10-5 [image]) producing characteristic changes in the ecg. (depression of the ST segment and T-waves, arrythmias and conduction disturbances have been observed also to cause a loss of K from cardiac muscle, and an inhibition of cholinesterase activity. The magnitude of the glycoside effect is dependent upon K and acetylcholine content of the medium. Increasing the K in the medium or addition of acetylcholine to the perfusion fluid diminishes these effects of lanatoside C. Lowering the K ion concn. of the medium enhances the effects of lanatoside C. A comparison of the effects of lanatoside C on the electrical properties and ion transfer of myocardial tissue with those of the typical inhibitors of cholinesterase suggest that the depression of the T_wave of the ecg. may be due to the inhibition of cholinesterase activity that occurs in the presence of the glycoside. It is suggested that the effects of lanatoside C on the R_ST segment may be due to the influence of the drug on some other metabolic process.