兔膀胱中缺乏力抑制与热休克蛋白20的低表达相关。
Absence of force suppression in rabbit bladder correlates with low expression of heat shock protein 20.
作者信息
Batts Timothy W, Walker John S, Murphy Richard A, Rembold Christopher M
机构信息
Cardiovascular Division, Department of Internal Medicine, University of Virginia, Charlottesville, Virginia 22908, USA.
出版信息
BMC Physiol. 2005 Nov 2;5:16. doi: 10.1186/1472-6793-5-16.
BACKGROUND
Nitroglycerin can induce relaxation of swine carotid artery without sustained reductions in [Ca2+]i or myosin regulatory light chain (MRLC) phosphorylation. This has been termed force suppression and been found to correlate with ser16-phosphorylation of heat shock protein 20 (HSP20). We tested for the existence of this mechanism in a smooth muscle that is not responsive to nitric oxide.
METHODS
Isometrically mounted mucosa free rabbit bladder strips were contracted with carbachol and relaxed with 8-Br-cGMP, forskolin, or isoprenaline.
RESULTS
Contraction was associated with a highly cooperative relation between MRLC phosphorylation and force such that very small increases in MRLC phosphorylation induced large increases in force. Relaxation induced by 8-Br-cGMP, forskolin, or isoprenaline did not shift the MRLC phosphorylation-force relation from that observed with carbachol alone, i.e. there was no force suppression. HSP20 content was negligible (approximately two hundred-fold less than swine carotid).
CONCLUSION
The lack of force suppression in the absence of HSP20 is consistent with the hypothesized role for HSP20 in the force suppression observed in tonic smooth muscles.
背景
硝酸甘油可诱导猪颈动脉舒张，而细胞内钙离子浓度（[Ca2+]i）或肌球蛋白调节轻链（MRLC）磷酸化并未持续降低。这一现象被称为力抑制，并且发现其与热休克蛋白20（HSP20）的丝氨酸16磷酸化相关。我们在对一氧化氮无反应的平滑肌中测试了这种机制的存在情况。
方法
将等长安装的无黏膜兔膀胱条用卡巴胆碱收缩，并用8-溴环磷酸鸟苷（8-Br-cGMP）、福斯高林或异丙肾上腺素舒张。
结果
收缩与MRLC磷酸化和力之间存在高度协同关系，以至于MRLC磷酸化的非常小的增加会引起力的大幅增加。8-Br-cGMP、福斯高林或异丙肾上腺素诱导的舒张并未使MRLC磷酸化-力关系偏离单独使用卡巴胆碱时观察到的关系，即不存在力抑制。HSP20含量可忽略不计（约比猪颈动脉少两百倍）。
结论
在缺乏HSP20的情况下无力抑制，这与HSP20在张力性平滑肌中观察到的力抑制中的假设作用一致。
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