Imaging and electrophysiological studies with APB. (A) Histogram showing that 10 μM APB did not affect Ca2+ mobilization by 30 μM CPA in the endothelium of the aortic valve, whereas 30 μM APB caused a significant reduction in the 380:340 fluorescent ratio that was insensitive to 100 μM 5-MTHF or (6R)-BH4.(B) Whole-cell patch-clamp recordings and histogram showing that 10 μM APB did not depress endothelial hyperpolarizations evoked by 30 μM CPA. (C and D) Original recordings and histogram showing that attenuation of CPA-evoked subintimal smooth muscle hyperpolarization by 10 μM APB was prevented by 100 μM 5-MTHF, (6R)-BH4,(6S)-BH4, or 2,000 units/ml catalase but not by 100 μM FA or BH2. *, P < 0.05, compared with control.