EFFECT OF BERBERINE ON CYTOSOLIC FREE CALCIUM OF RAT MYOCARDIAL CELLS IN VITRO

In order to verify the inotropic effect of berberine (Ber) on myocardial tissues, the effect of Ber on cytosolic free calcium Ca²⁺i in cultured rat single myocardial cells were examined by using Fura-2/AM and AR-CM-MIC cation measurement system. Ber (10～400 μmol·L^-1) was found to increase the resting Ca²⁺i and saturate at about 200 μmol·L^-1. The Ca²⁺i increase was not depressed by atropine, phentolamine, propranolol and tetrodotoxin, but was inhibited by verapamil (Ver) 3 μmol·L^-1 or CoCl₂ 10 mmol·L^-1. The Ca²⁺i increase induced by Ber (30 μmol·L^-1) added to stimulating agents as KCl, CaCl₂, NE or Oua was stronger than that induced by stimulating agents only and Ver 3 μmol·L^-1 still showed inhibitory effects on the Ca²⁺i increase. Under Ca²⁺free or Ca²⁺, K⁺, Na⁺-free conditions, Ber (30～200 μmol·L^-1) still showed ascending effects on Ca²⁺i, and Ver 3 μmol·L^-1 only inhibited the Ber effects in Ca²⁺-free condition. The results suggest that Ber might induce moderate Ca²⁺i increase via Ca²⁺ influx and intracellular Ca²⁺ release, and show positive inotropic effect.