Abstract: Objective To investigate the effects of hypaconitine on cardiac conduction function and hERG channels, and to elucidate the potential mechanisms underlying cardiotoxicity. Methods Langendorff isolated heart perfusion combined with electrical mapping technology was used to assess changes in cardiac conduction function. Whole-cell patch-clamp techniques were employed to evaluate the effects of hypaconitine on hERG channel currents in hERG-HEK293 cells. Western blot analysis was performed to examine the expression levels of the proteins. Results Electrical mapping experiments revealed that hypaconitine exhibited significant dose-dependent cardiotoxicity. Concentrations above 25 nmol·L^-1 disrupted cardiac conduction function, characterized by altered conduction direction, increased heart rate, prolonged conduction time, and reduced conduction velocity. At concentrations of 100 to 150 nmol·L^-1,ventricular fibrillation could be induced. Moreover, a 15-min perfusion with 25 nmol·L^-1 hypaconitine prolonged the QTc interval. Patch-clamp experiments showed that the half-maximal inhibitory concentration (IC₅₀) of hypaconitine on hERG channels was 34.34 μmol·L^-1. Western blot analysis demonstrated that 200 μmol·L^-1 hypaconitine significantly decreased the expressions of mature hERG protein (relative molecular mass: 155 000) and inhibited the phosphorylation of PKA. Conclusion The effect of hypaconitine on hERG channels is not the leading contributor to cardiac conduction dysfunction in guinea pigs.

Key words: Hypaconitine, Cardiac Mapping, hERG Channel, hERG Protein Expression, Protein Kinase A (PKA), Guinea Pig