PURPOSE: We examined the role of the modulation of Ca2+ sensitivity for regulating the contractility of corpus cavernosum smooth muscle. MATERIALS AND METHODS: We applied simultaneous measurements of intracellular Ca2+ concentration and tension in fura-PE3 loaded intact strips and receptor coupled permeabilization by alpha-toxin. RESULTS: In intact fura-PE3 loaded strips the tension induced by 10 microM. phenylephrine was significantly greater than that produced by depolarization with 118 mM. K+, although the extent of intracellular Ca2+ concentration elevations was similar. During sustained contraction induced by 10 microM. phenylephrine the application of 10 microM. Y-27632 (a Rho kinase inhibitor) induced relaxation with a slight decrease in intracellular Ca2+ concentration, while the application of 3 microM. GF109203X (a protein kinase C inhibitor) induced relaxation without changing intracellular Ca2+ concentration. In alpha-toxin permeabilized strips 10 microM. phenylephrine induced a larger increase in force at a constant intracellular Ca2+ concentration and produced a leftward shift in the intracellular Ca2+ concentration-tension relationship, a response that was partially inhibited by pretreatment with Y-27632 or GF109203X. CONCLUSIONS: These results indicate that in rabbit corpus cavernosum smooth muscle phenylephrine induces contraction not only by increasing intracellular Ca2+ concentration, but also by increasing Ca2+ sensitivity of the contractile apparatus in a Rho kinase and protein kinase C dependent manner. Antagonism of Ca2+ sensitization pathways in the corpus cavernosum smooth muscle represents an alternate target for the treatment of erectile dysfunction.
PURPOSE: We examined the role of the modulation of Ca2+ sensitivity for regulating the contractility of corpus cavernosum smooth muscle. MATERIALS AND METHODS: We applied simultaneous measurements of intracellular Ca2+ concentration and tension in fura-PE3 loaded intact strips and receptor coupled permeabilization by alpha-toxin. RESULTS: In intact fura-PE3 loaded strips the tension induced by 10 microM. phenylephrine was significantly greater than that produced by depolarization with 118 mM. K+, although the extent of intracellular Ca2+ concentration elevations was similar. During sustained contraction induced by 10 microM. phenylephrine the application of 10 microM. Y-27632 (a Rho kinase inhibitor) induced relaxation with a slight decrease in intracellular Ca2+ concentration, while the application of 3 microM. GF109203X (a protein kinase C inhibitor) induced relaxation without changing intracellular Ca2+ concentration. In alpha-toxin permeabilized strips 10 microM. phenylephrine induced a larger increase in force at a constant intracellular Ca2+ concentration and produced a leftward shift in the intracellular Ca2+ concentration-tension relationship, a response that was partially inhibited by pretreatment with Y-27632 or GF109203X. CONCLUSIONS: These results indicate that in rabbit corpus cavernosum smooth muscle phenylephrine induces contraction not only by increasing intracellular Ca2+ concentration, but also by increasing Ca2+ sensitivity of the contractile apparatus in a Rho kinase and protein kinase C dependent manner. Antagonism of Ca2+ sensitization pathways in the corpus cavernosum smooth muscle represents an alternate target for the treatment of erectile dysfunction.
Authors: Otacilio D Benvindo; Nilberto Rf Nascimento; Claudia F Santos; Manasses C Fonteles; Edilberto R Silveira; Daniel E Uchoa; Adriana R Campos; Karina Ma Cunha; Flavia A Santos; Vietla S Rao Journal: Asian J Androl Date: 2011-07-18 Impact factor: 3.285
Authors: Yong Sun Choi; Sang Kuon Lee; Woong Jin Bae; Su Jin Kim; Hyuk Jin Cho; Sung-Hoo Hong; Ji Youl Lee; Tae-Kon Hwang; Sae Woong Kim Journal: PLoS One Date: 2014-08-19 Impact factor: 3.240