Electrophysiologic properties of isolated adult cardiomyocytes from septic rats

In this study, we examined the effect of sepsis on the electrical properties of isolated ventricular myocytes. Sepsis was induced by cecal ligation and puncture (CLP). The control rats were sham-operated. Membrane potentials and ionic currents in isolated cardiac myocytes were measured by the tight-seal, whole-cell patch-clamp technique. The results show that the resting membrane potentials of heart cells were significantly lower in the septic group (18 hr post-CLP) than those in the control group. However, there was no significant difference in action potential duration of 50% and 90% repolarization between the two groups of cells. In voltage-clamp experiments, isoproterenol (10 nM), a beta-adrenergic agonist, caused an increase in L-type calcium current (ICa,L) in a similar magnitude in myocytes isolated from the control and septic rats. Furthermore, isoproterenol failed to modify the time constants for ICa,L inactivation and the overall shape of current-voltage relationship for both groups of cells. These results indicate that formation of a G omega seal and subsequent tight-seal whole-cell recording with patch-clamp technique can be performed in heart cells derived from CLP-induced septic rats, and that septic rat heart is capable of responding effectively to beta-adrenergic stimulation.