P4 inhibits BPA-induced triggered activities in isolated female rat ventricular myocytes. (a) Left: Representative contraction traces under control (Cont), BPA, and BPA + P4. Red arrows indicate spontaneous after-contraction (i.e., triggered activity) after pacing. Right: Percentages of myocytes with triggered activities under indicated treatments (n = 30 to 50 myocytes for each group from four hearts). (b) Representative confocal images of Ca²⁺ transients in myocytes elicited by repeated pacing under various treatments. Red arrows indicate spontaneous Ca²⁺ after-transients (i.e., triggered activity) after pacing. For all experiments, BPA and P4 = 1 nM; RU486 = 1 μM. **P < 0.01; ^#P > 0.1 versus control; ^†P < 0.01. NS, not significant (χ² test).