Studies of the effect of antiarrhythmic drugs on carbohydrate metabolism of rat heart muscle in vitro

Mechanobiology Assays with Applications in Cardiomyocyte Biology and Cardiotoxicity

Cardiomyocytes are the motor units that drive the contraction and relaxation of the heart. Traditionally, testing of drugs for cardiotoxic effects has relied on primary cardiomyocytes from animal models and focused on short-term, electrophysiological, and arrhythmogenic effects. However, primary cardiomyocytes present challenges arising from their limited viability in culture, and tissue from animal models suffers from a mismatch in their physiology to that of human heart muscle. Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) can address these challenges. They also offer the potential to study not only electrophysiological effects but also changes in cardiomyocyte contractile and mechanical function in response to cardiotoxic drugs. With growing recognition of the long-term cardiotoxic effects of some drugs on subcellular structure and function, there is increasing interest in using hiPSC-CMs for in vitro cardiotoxicity studies. This review provides a brief overview of techniques that can be used to quantify changes in the active force that cardiomyocytes generate and variations in their inherent stiffness in response to cardiotoxic drugs. It concludes by discussing the application of these tools in understanding how cardiotoxic drugs directly impact the mechanobiology of cardiomyocytes and how cardiomyocytes sense and respond to mechanical load at the cellular level.

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

1. The influence of antifibrillatory agents on the release of previously accumulated (86)Rb(+) 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 (86)Rb release. The concentration-response curves for both the mechanical effect and the influence on (86)Rb 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.