Fernandes Vítor S, Xin Wenkuan, Petkov Georgi V
Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina.
Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina
Am J Physiol Cell Physiol. 2015 Jul 15;309(2):C107-16. doi: 10.1152/ajpcell.00021.2015. Epub 2015 May 6.
Hydrogen sulfide (H2S) is a key signaling molecule regulating important physiological processes, including smooth muscle function. However, the mechanisms underlying H2S-induced detrusor smooth muscle (DSM) contractions are not well understood. This study investigates the cellular and tissue mechanisms by which H2S regulates DSM contractility, excitatory neurotransmission, and large-conductance voltage- and Ca(2+)-activated K(+) (BK) channels in freshly isolated guinea pig DSM. We used a multidisciplinary experimental approach including isometric DSM tension recordings, colorimetric ACh measurement, Ca(2+) imaging, and patch-clamp electrophysiology. In isolated DSM strips, the novel slow release H2S donor, P-(4-methoxyphenyl)-p-4-morpholinylphosphinodithioic acid morpholine salt (GYY4137), significantly increased the spontaneous phasic and nerve-evoked DSM contractions. The blockade of neuronal voltage-gated Na(+) channels or muscarinic ACh receptors with tetrodotoxin or atropine, respectively, reduced the stimulatory effect of GYY4137 on DSM contractility. GYY4137 increased ACh release from bladder nerves, which was inhibited upon blockade of L-type voltage-gated Ca(2+) channels with nifedipine. Furthermore, GYY4137 increased the amplitude of the Ca(2+) transients and basal Ca(2+) levels in isolated DSM strips. GYY4137 reduced the DSM relaxation induced by the BK channel opener, NS11021. In freshly isolated DSM cells, GYY4137 decreased the amplitude and frequency of transient BK currents recorded in a perforated whole cell configuration and reduced the single BK channel open probability measured in excised inside-out patches. GYY4137 inhibited spontaneous transient hyperpolarizations and depolarized the DSM cell membrane potential. Our results reveal the novel findings that H2S increases spontaneous phasic and nerve-evoked DSM contractions by activating ACh release from bladder nerves in combination with a direct inhibition of DSM BK channels.
硫化氢（H₂S）是一种调节重要生理过程（包括平滑肌功能）的关键信号分子。然而，H₂S诱导逼尿肌平滑肌（DSM）收缩的潜在机制尚未完全明确。本研究探讨了H₂S调节DSM收缩性、兴奋性神经传递以及新鲜分离的豚鼠DSM中大通量电压和Ca²⁺激活的K⁺（BK）通道的细胞和组织机制。我们采用了多学科实验方法，包括等长DSM张力记录、比色法乙酰胆碱（ACh）测量、Ca²⁺成像和膜片钳电生理学。在分离的DSM条带上，新型缓释H₂S供体P-(4-甲氧基苯基)-p-4-吗啉基膦二硫代酸吗啉盐（GYY4137）显著增加了自发性相性和神经诱发的DSM收缩。分别用河豚毒素或阿托品阻断神经元电压门控Na⁺通道或毒蕈碱型ACh受体，可降低GYY4137对DSM收缩性的刺激作用。GYY4137增加了膀胱神经释放的ACh，而用硝苯地平阻断L型电压门控Ca²⁺通道后，这种增加受到抑制。此外，GYY4137增加了分离的DSM条带中Ca²⁺瞬变的幅度和基础Ca²⁺水平。GYY4137降低了BK通道开放剂NS11所诱导的DSM舒张。在新鲜分离的DSM细胞中，GYY4137降低了在穿孔全细胞配置中记录的瞬时BK电流的幅度和频率，并降低了在切除的内向外膜片中测量的单个BK通道开放概率。GYY4137抑制自发性瞬时超极化并使DSM细胞膜电位去极化。我们的结果揭示了新的发现，即H₂S通过激活膀胱神经释放ACh并直接抑制DSM BK通道，增加自发性相性和神经诱发的DSM收缩。
