Department of Cell Physiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
Br J Pharmacol. 2009 Dec;158(8):2030-45. doi: 10.1111/j.1476-5381.2009.00514.x.
We investigated the cellular mechanisms underlying spontaneous contractions in the mouse renal pelvis, regulated by calcitonin gene-related peptide (CGRP).
Spontaneous contractions, action potentials and Ca2+ transients in typical and atypical smooth muscle cells (TSMCs and ATSMCs) within the renal pelvis wall were recorded separately using tension and intracellular microelectrode recording techniques and Fluo-4 Ca2+ imaging. Immunohistochemical and electron microscopic studies were also carried out.
Bundles of CGRP containing transient receptor potential cation channel, subfamily V, member 1-positive sensory nerves were situated near both TSMCs and ATSMCs. Nerve stimulation reduced the frequency but augmented the amplitude and duration of spontaneous phasic contractions, action potentials and Ca2+ transients in TSMCs. CGRP and agents increasing internal cyclic adenosine monophosphate (cAMP) mimicked the nerve-mediated modulation of TSMC activity and suppressed ATSMCs Ca2+ transients. Membrane hyperpolarization induced by CGRP or cAMP stimulators was blocked by glibenclamide, while their negative chronotropic effects were less affected. Glibenclamide enhanced TSMC Ca2+ transients but inhibited ATSMC Ca2+ transients, while both 5-hydroxydecanoate and diazoxide, a blocker and opener of mitochondrial ATP-sensitive K+ channels, respectively, reduced the Ca2+ transient frequency in both TSMCs and ATSMCs. Inhibition of mitochondrial function blocked ATSMCs Ca2+ transients and inhibited spontaneous excitation of TSMCs.
The negative chronotropic effects of CGRP result primarily from suppression of ATSMC Ca2+ transients rather than opening of plasmalemmal ATP-sensitive K+ channels in TSMCs. The positive inotropic effects of CGRP may derive from activation of TSMC L-type Ca2+ channels. Mitochondrial Ca2+ handling in ATSMCs also plays a critical role in generating Ca2+ transients.
我们研究了降钙素基因相关肽（CGRP）调节的小鼠肾盂自发性收缩的细胞机制。
使用张力和细胞内微电极记录技术以及 Fluo-4 Ca2+成像技术，分别记录肾盂壁内典型和非典型平滑肌细胞（TSMCs 和 ATSMCs）的自发性收缩、动作电位和 Ca2+瞬变。还进行了免疫组织化学和电子显微镜研究。
含有瞬时受体电位阳离子通道，亚家族 V，成员 1 阳性感觉神经的 CGRP 束位于 TSMC 和 ATSMC 附近。神经刺激降低了 TSMC 自发性相位收缩、动作电位和 Ca2+瞬变的频率，但增加了幅度和持续时间。CGRP 和增加细胞内环腺苷酸（cAMP）的试剂模拟了神经对 TSMC 活性的调节，并抑制了 ATSMCs 的 Ca2+瞬变。CGRP 或 cAMP 刺激物引起的膜超极化被格列本脲阻断，而其负性变时作用受影响较小。格列本脲增强了 TSMC 的 Ca2+瞬变，但抑制了 ATSMC 的 Ca2+瞬变，而 5-羟基癸酸和二氮嗪，分别是线粒体 ATP 敏感性 K+通道的阻断剂和开放剂，均降低了 TSMC 和 ATSMC 中 Ca2+瞬变的频率。线粒体功能抑制阻断了 ATSMCs 的 Ca2+瞬变并抑制了 TSMCs 的自发性兴奋。
CGRP 的负性变时作用主要源于抑制 ATSMC 的 Ca2+瞬变，而不是 TSMCs 质膜 ATP 敏感性 K+通道的开放。CGRP 的正性变力作用可能来自于 TSMC L 型 Ca2+通道的激活。ATSMCs 中的线粒体 Ca2+处理在产生 Ca2+瞬变方面也起着关键作用。
