Acidosis Inhibits Gallbladder Contraction Mediated by Protein Kinase C Activation

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The effects of extracellular acidosis on gallbladder contraction were investigated using gallbladder strips isolated from guinea pigs. In an acidic medium (pH 6.9), gallbladder contraction induced by histamine and prostaglandin E₂ was significantly lower than that in a normal medium (pH 7.4). Acidosis affected neither gallbladder contraction induced by histamine in the absence of extracellular Ca²⁺ nor that induced by KCl. Acidosis significantly inhibited Ca²⁺-induced contraction in the presence of sodium fluoride and phorbol 12,13-dibutyrate but not that in the presence of KCl. Staurosporine (30 nM) significantly inhibited gallbladder contraction induced by histamine and prostaglandin E₂, but not that by KCl. Histamine-induced contraction in the presence of staurosporine was not affected by acidosis. Acidosis significantly inhibited Ca²⁺-induced contraction in the presence of histamine but not that in the presence of both histamine and staurosporine. These results suggest that extracellular acidosis selectively inhibits gallbladder contraction mediated by protein kinase C activation.