Contribution of Rho-kinase in human gallbladder contractions

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Rho/Rho-kinase-mediated pathway has been involved in a variety of physiological processes, including Ca 2+ sensitization, which enhances smooth muscle contraction. In this study, first of all we investigated the expression of Rho-kinase (ROCK-2) and then the role of this protein in the control of smooth muscle contraction in the isolated human gallbladder. For this purpose, we examined the effects of a selective Rho-kinase inhibitor, (+)- ( R)- trans-4-(1-aminoethyl)- N-(4-pyridyl) cyclohexanecarboxamide dihydrochloride monohydrate (Y-27632, 10 − 8 − 3 × 10 − 5 M) on carbachol (10 − 8 –10 − 4 M), cholecystokinin-8 (10 − 8 M), endothelin-1 (10 − 8 M), histamine (10 − 5 M), neurokinin A (10 − 7 –10 − 6 M), 5-hydroxytryptamine (10 − 6 –10 − 5 M) and potassium chloride (KCl, 25–50 mM)-induced contractions as well as spontaneous contractile activity. Y-27632 (10 − 5 M) significantly reduced 5-hydroxytryptamine, neurokinin A and KCl-induced contractions. Moreover, this Rho-kinase inhibitor (10 − 8 − 3 × 10 − 5 M, cumulatively) relaxed the contractions produced by cholecystokinin-8, endothelin-1 and histamine in a concentration-dependent manner, being the pEC 50 values for Y-27632 5.74 ± 0.12, 5.33 ± 0.09 and 5.95 ± 0.18, respectively. Carbachol (10 − 8 –10 − 4 M) pfroduced concentration-dependent contractions, which were also inhibited significantly by Y-27632. In addition, the spontaneous contractile activity was suppressed in the presence of Y-27632 (10 − 6 –10 − 5 M). Moreover, Western blot analysis has revealed that Rho-kinase is expressed in homogenates of the human gallbladder. Taken together, these results show that Rho-kinase is expressed in the human gallbladder, and it has an essential role in agonists and depolarization-induced contractions as well as spontaneous contractile activity.