The inhibitory effect of the flavonoid galangin on urinary bladder smooth muscle contractility is mediated in part by modulation of Ca2+ release from intracellular stores

The present study was designed to examine the effect of the flavonoid galangin on the muscarinic receptor mediating a carbachol-induced contraction and to investigate the effect of the flavonoid on Ca2+ release from intracellular stores in the urinary bladder of the pig. Galangin (10(-7) - 10(-4) M) produced a concentration-dependent inhibition of the contractile responses to electrical field stimulation (EFS) and carbachol (10(-5) M). Galangin (3 x 10(-5) M) reduced muscle contractions evoked by carbachol (10(-5) M) in calcium-containing solution as well as contractions evoked by carbachol and caffeine (2 x 10(-2) M) in Ca2+-free solutions significantly. The flavonoid had a stronger effect on the maximal force of the contractions induced by caffeine, compared to contractions induced by carbachol. These results suggest that galangin has an important effect on the intracellular calcium mobilization, which might be attributed predominantly to its influence on ryanodine-receptors.