Aim: To investigate the effects and mechanism of berberine (Ber) on the intracellular free calcium concentration ([Ca2+]i) in the smooth muscle cells of guinea pig colon. Methods: The changes of [Ca2+]i were assayed by the biwavelength spectrophotometry with Fura 2-AM in the cell suspension of the smooth muscle cells, which were freshly isolated from guinea pig colon. Results: In the resting state, [Ca2+]i in the HEPES-Ringer solution (CaCl2 1.5 mmol·l–1) was (108 ± 9.4) nmol·l–1 (n = 7). Ber had no significant effects on the resting [Ca2+]i, but markedly inhibited the increase in [Ca2+]i induced by 60 mmol·l–1 KCl in a concentration-dependent manner. The value of IC50 was 34.09 µmol·l–1. 30 and 100 µmol·l–1 Ber also inhibited the elevation of [Ca2+]i evoked by 10 µmol·l–1 Ach in a dose-dependent fashion in the presence or absence of extracellular Ca2+. In addition, Ber inhibited the elevation of [Ca2+]i stimulated by cyclopiazonic acid (CPA) in a dose-dependent manner. This effect was more potent in the HEPES-Ringer solution (IC50 = 37.79 µmol·l–1) than Ca2+-free medium (IC50 = 49.70 µmol·l–1). Conclusions: Ber possessed an inhibitory effect on the influx of extracellular Ca2+ and Ca2+-release from intracellular stores in the smooth muscle cells of colon. That is to say Ber may be a blocker of Ca2+ channels.

Journal Section:
Original Paper: Colon
Keywords:
Berberine, Colon, Smooth muscle cell, Fura-2, Intracellular free calcium, Acetylcholine, Cyclopiazonic acid, Ca2+ channel blocker
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© 2001 S. Karger AG, Basel
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