Additional similarity of cardiac cAMP-activated Cl- channels to CFTR Cl- channels

Isoproterenol, forskolin, or cAMP activated a time-independent Cl- current (ICl.cAMP), which is known to be activated by A-kinase-mediated phosphorylation, in guinea pig ventricular myocytes. External glibenclamide inhibited ICl.cAMP in a concentration-dependent manner with IC50 of around 30 microM. Thus, it is concluded that glibenclamide inhibits cardiac cAMP-activated Cl- channels and that the Cl- channel is, in this respect, similar to epithelial CFTR Cl- channel. Northern analysis actually indicated that CFTR messenger RNA is expressed in the guinea pig ventricle.