Hockey J S, Wu C, Fry C H
The Institute of Urology & Nephrology, London, UK.
BJU Int. 2000 Sep;86(4):531-7. doi: 10.1046/j.1464-410x.2000.00773.x.
To determine the important cellular site(s) of action of a brief exposure to NaCN (chosen to reduce mitochondrial respiration and hence mimic cellular hypoxia) on the mechanical properties and regulation of intracellular [Ca2+] in human detrusor smooth muscle. Using muscle samples obtained from patients with stable and unstable bladders, to determine whether the unstable bladder is associated with changes in the functional properties of detrusor muscle under these circumstances. Materials and methods Experiments were conducted in vitro on muscle strips or isolated cells. Isometric tension was recorded in muscle strips during electrical stimulation or exposure to agonists. Intracellular [Ca2+] and [H+] were measured by epifluorescence microscopy, and cell autofluorescence measured as an index of mitochondrial function.
There were no differences in the responses to electrical stimulation and varying concentrations of carbachol in muscle strips from stable and unstable bladders. NaCN (2 mmol/L) reduced the contraction induced by carbachol (10 micromol/L) by a mean (SD) of 43 (16)% and 56 (15)% in the two groups; the reduction in the unstable was significantly less than in the stable group. NaCN similarly reduced the response to 10 mmol/L caffeine, but had no effect on the KCl-induced contraction. NaCN significantly increased the resting sarcoplasmic [Ca2+] and attenuated the calcium transients evoked by carbachol and caffeine, but again had no effect on the KCl-induced transient. The reduction of the carbachol calcium transient was also less in cells from unstable bladders than in those from stable bladders. There was no effect of NaCN on intracellular pH, except for a brief, transient alkalosis.
NaCN reduces both the contraction and Ca-transient to carbachol by reducing Ca2+ accumulation by intracellular stores, because the carbachol- and caffeine-evoked responses were similar. Any effect on transmembrane Ca2+ flux was minimal because there was no effect on KCl-induced responses. The greater resilience of tissue from unstable bladders to acute cellular hypoxia may reflect some adaptation acquired in vivo.
确定短期暴露于氰化钠（选择其来降低线粒体呼吸，从而模拟细胞缺氧）对人逼尿肌平滑肌力学特性及细胞内[Ca2+]调节的重要作用位点。利用从稳定膀胱和不稳定膀胱患者获取的肌肉样本，确定在这些情况下不稳定膀胱是否与逼尿肌功能特性的变化相关。材料与方法实验在体外对肌肉条或分离细胞进行。在电刺激或暴露于激动剂期间记录肌肉条的等长张力。通过落射荧光显微镜测量细胞内[Ca2+]和[H+]，并测量细胞自发荧光作为线粒体功能指标。
稳定膀胱和不稳定膀胱的肌肉条对电刺激及不同浓度卡巴胆碱的反应无差异。氰化钠（2 mmol/L）使两组中卡巴胆碱（10 μmol/L）诱导的收缩分别平均（标准差）降低43（16）%和56（15）%；不稳定组的降低幅度显著小于稳定组。氰化钠同样降低了对10 mmol/L咖啡因的反应，但对氯化钾诱导的收缩无影响。氰化钠显著增加静息肌浆[Ca2+]，并减弱卡巴胆碱和咖啡因诱发的钙瞬变，但同样对氯化钾诱导的瞬变无影响。不稳定膀胱细胞中卡巴胆碱钙瞬变的降低幅度也小于稳定膀胱细胞。除短暂的一过性碱中毒外，氰化钠对细胞内pH无影响。
氰化钠通过减少细胞内钙库的Ca2+蓄积，降低对卡巴胆碱的收缩及钙瞬变，因为卡巴胆碱和咖啡因诱发的反应相似。对跨膜Ca2+通量的任何影响极小，因为对氯化钾诱导的反应无影响。不稳定膀胱组织对急性细胞缺氧的更大恢复力可能反映了体内获得的某种适应性变化。
