Novel role for the transient potential receptor melastatin 4 channel in guinea pig detrusor smooth muscle physiology

作者：Smith Amy C; Hristov Kiril L; Cheng Qiuping; Xin Wenkuan; Parajuli Shankar P; Earley Scott; Malysz John; Petkov Georgi V^*

来源：American Journal of Physiology - Cell Physiology, 2013, 304(5): C467-C477.

DOI：10.1152/ajpcell.00169.2012

• 9-phenanthrol
• TRP channel
• urinary bladder
• patch-clamp

Smith AC, Hristov KL, Cheng Q, Xin W, Parajuli SP, Earley S, Malysz J, Petkov GV. Novel role for the transient potential receptor melastatin 4 channel in guinea pig detrusor smooth muscle physiology. Am J Physiol Cell Physiol 304: C467-C477, 2013. First published January 9, 2013; doi:10.1152/ajpcell.00169.2012.-Members of the transient receptor potential (TRP) channel superfamily, including the Ca2+ -activated monovalent cation-selective TRP melastatin 4 (TRPM4) channel, have been recently identified in the urinary bladder. However, their expression and function at the level of detrusor smooth muscle (DSM) remain largely unexplored. In this study, for the first time we investigated the role of TRPM4 channels in guinea pig DSM excitation-contraction coupling using a multidisciplinary approach encompassing protein detection, electrophysiology, live-cell Ca2+ imaging, DSM contractility, and 9-phenanthrol, a recently characterized selective inhibitor of the TRPM4 channel. Western blot and immunocytochemistry experiments demonstrated the expression of the TRPM4 channel in whole DSM tissue and freshly isolated DSM cells with specific localization on the plasma membrane. Perforated whole cell patch-clamp recordings and real-time Ca2+ imaging experiments with fura 2-AM, both using freshly isolated DSM cells, revealed that 9-phenanthrol (30 mu M) significantly reduced the cation current and decreased intracellular Ca2+ levels. 9-Phenanthrol (0.1-30 mu M) significantly inhibited spontaneous, 0.1 mu M carbacholinduced, 20 mM KCl-induced, and nerve-evoked contractions in guinea pig DSM-isolated strips with IC50 values of 1-7 mu M and 70-80% maximum inhibition. 9-Phenanthrol also reduced nerveevoked contraction amplitude induced by continuous repetitive electrical field stimulation of 10-Hz frequency and shifted the frequencyresponse curve (0.5-50 Hz) relative to the control. Collectively, our data demonstrate the novel finding that TRPM4 channels are expressed in guinea pig DSM and reveal their critical role in the regulation of guinea pig DSM excitation-contraction coupling.

• 出版日期2013-3