Magnesium lithospermate B decreases [Ca2+]i in endothelial cells by inhibiting K+ currents

Magnesium lithospermate B (MLB) is a hydrophilic active component of Salviae miltiorrhizae Radix. Studies have shown that MLB affected intracellular calcium ([Ca2+]i), but the underlying mechanism was unclear yet. The present work was aimed to investigate the underlying mechanism of MLB affecting [Ca2+]i in endothelial cells (ECs). Isolated mesentery arteries were employed to test the involvement of L-Ca2+ channel. [Ca2+]i was measured in ECs loaded with Fluo-3. Membrane potential and membrane currents were recorded in ECs using patch-clamp techniques. Results showed that MLB did not inhibit Ca2+ influx via L-Ca2+ channel in isolated mesenteric arteries. However, MLB decreased [Ca2+]i in a concentration-dependent manner in ECs. MLB depolarized the membrane potential of ECs and inhibited K+ currents. These results demonstrated that MLB decreased [Ca2+]i by inhibiting K+ currents and depolarizing membrane potential in ECs.