Pharmacological evidence for calcium channel inhibition by Danshen (Salvia miltiorrhiza) on rat isolated femoral artery

This study investigated the relaxant actions of Danshen (Salvia miltiorrhiza) and its lipid-soluble- and water-soluble-fractions on endothelium-denuded rat isolated femoral artery rings. Danshen, its water-soluble fraction and its lipid-soluble fraction produced relaxation of the phenylephrine-precontracted artery rings with IC50 values of 149 +/- 20 mu g/mL, 160 +/- 25 mu g/mL, and 23 +/- 6 mu g/mL respectively. Pretreatment of the artery rings with a non-Selective potassium channel inhibitor tetraethylammonium (TE (A) over bar 10 mM) produced a significant two-fold rightward shift of the concentration-response curve to Danshen and a four-fold shift to its water-soluble fraction, but had no effect on the lipid-soluble fraction. A 3.3-fold shift was produced on the concentration-response curve of Danshen when the artery rings were pretreated with a mixture of 10 mM TEA, 1 mM 4-aminopyridine (K-V blocker), 1 mu M glibenclamide (K-ATP blocker), 100 nM iberiotoxin (BKCa blocker), and 100 mu M barium chloride (K-IR blocker). Involvement of Ca2+ channels was investigated in endothelium-denuded artery rings incubated with Ca2+-tree buffer and primed with 1 mu M phenylephrine or 60 mM KCl for 5 minutes prior to adding CaCl2 to elicit contraction. In artery rings primed with phenylephrine, pretreatment with I mg/mL Danshen, 1 mg/mL water-soluble fraction of Danshen, 0.1 mg/mL lipid-soluble traction of Danshen, and 100 nM nifedipine abrogated the CaCl2-induced contraction. On the other hand, in artery rings primed with KCl, these agents produced 40%, 25%, 53%, and 92% inhibition on the maximum contraction induced by CaCl2, respectively. Increasing the concentrations of Danshen and its water-soluble fraction to 3 mg/mL, and the lipid-soluble fraction to 0.3 mg/mL farther reduced the maximum contraction to 92%, 93%, and 83%, respectively. Taken together, these findings suggested the vasorelaxant actions of Danshen and its fractions were produced primarily by inhibition of Ca2+ flux in the vascular smooth muscle cells and a small component was mediated by the opening of K+ channels.