Actions of the antiarrhythmic peptide AAP10 on intercellular coupling.

Disturbances in gap junction distribution and a decrease in the connexin43 content of the heart were shown to occur after myocardial infarction and in ischemic heart disease, respectively. These changes are now thought to play an important role in the genesis of arrhythmias associated with these diseases. It is thought that agents that can increase cellular coupling might be beneficial in these situations. Recently, we presented data showing that the synthetic peptide AAP10 acts antiarrhythmically in a model of regional ischemia. The data suggested that AAP10 might act via an increase in cellular coupling. The goal of this study was to establish whether AAP10 can interact with cardiac gap junctions. Measurements of the stimulus-response-interval (SRI) in guinea pig papillary muscle showed that high concentrations of AAP10 (1 microM) can decrease the SRI by about 10% under normoxic conditions. At lower concentrations (10 nM) AAP10 had no effect on SRI under normoxic conditions but prevented the increase in the SRI induced by perfusion with hypoxic, glucose-free Tyrode's solution. Double-cell voltage-clamp experiments confirmed that AAP10 can interact with cardiac gap junctions. 10 nM AAP10 could either diminish or reverse the run-down of gap junction conductance normally observed in pairs of guinea pig ventricular myocytes. During control gap junction conductance decreased with a rate of -2.5 +/- 2.0 nS/min. After application of 10 nM AAP10 gap junction conductance increased with a rate of +1.0 +/- 0.7 nS/min (p < 0.01). After washout of AAP10 gap junction conductance decreased again with a rate not significantly different from control. Our results show that AAP10 does interact with gap junctions. Because no other effects of AAP10 on other electrophysiological parameters could be found, this action on gap junctions might be the basis of AAP10's antiarrhythmic effect seen in previous studies.