Activation of the iberiotoxin-sensitive BKCa channels by salvianolic acid B of the porcine coronary artery smooth muscle cells

In this study, we examined the effects of Salvia miltiorrhiza (Danshen) crude extract, some of its lipid-soluble components (tanshinone I, tanshinone IIA, cryptotanshinone, dihydroisotanshinone I) and the water-soluble compounds (danshensu and salvianolic acid B) on the K+ channels such as the iberiotoxin-sensitive Ca2+-activated K+ (BKCa) channels and the glibenclamide-sensitive ATP-dependent K+ (IKATP) channels of the porcine left anterior descending coronary artery smooth muscle cells. Cumulative application of salvianolic acid B (30–300 μM) caused a l-NNA (100 μM)-insensitive, potentiation of the outward BKCa current amplitude with no apparent effect on the IKATP channels opening. Salvianolic acid B (300 μM) caused an ODQ (10 μM, a guanylate cyclase inhibitor)-sensitive enhancement of the outward BKCa current amplitude. In contrast, none of the other isolated chemical constituents of S. miltiorrhiza modified the openings of the two types of K+ channels studied. In conclusion, our results suggest that salvianolic acid B, a major hydrophilic constituent found in Radix S. miltiorrhiza, activated the opening of the BKCa channels of the porcine coronary artery smooth muscle cells through the activation of guanylate cyclase without the involvement of the nitric oxide synthase activation.