Rüegg J C, Sparrow M P, Mrwa U
Pflugers Arch. 1981 May;390(2):198-201. doi: 10.1007/BF00590207.
Smooth muscle from guinea pig taenia coli was chemically skinned with Triton X-100 and stored in ATP-salt solution containing 50% glycerol at -20 degrees C. Fiber bundles were relaxed at Ca2+-concentrations below 10(-7) M, but contracted at 10(-6) M Ca2+. The isometric tension developed could be partly relaxed by the addition of c-AMP (in the presence of NaF), and it could also be inhibited following preincubation with the catalytic subunit of c-AMP dependent protein kinase. The inhibitory effect was much more pronounced at intermediate Ca2+-concentrations (e.g. 10(-6)) than at concentrations producing a maximum contraction, suggesting that Ca-sensitivity had been lowered. Sodium fluoride which was required to potentiate the c-AMP effects was found to have a slight relaxing effect per se. The c-AMP effect may be mediated through activation of cyclic AMP-dependent kinase, producing, phosphorylation of the myosin light chain kinase which, according to Adelstein et al. (1978), may result in a net dephosphorylation of the myosin light chains and a concomittant inhibition of the contractile response.
用Triton X-100对豚鼠结肠带的平滑肌进行化学去膜处理，并保存在含有50%甘油的ATP盐溶液中，于-20℃下储存。纤维束在Ca2+浓度低于10^(-7) M时松弛，但在10^(-6) M Ca2+时收缩。所产生的等长张力可通过添加c-AMP（在NaF存在下）部分松弛，并且在用c-AMP依赖性蛋白激酶的催化亚基预孵育后也可被抑制。在中等Ca2+浓度（例如10^(-6)）下，抑制作用比在产生最大收缩的浓度下更为明显，这表明Ca2+敏感性降低。发现增强c-AMP作用所需的氟化钠本身具有轻微的松弛作用。c-AMP的作用可能是通过激活环AMP依赖性激酶介导的，产生肌球蛋白轻链激酶的磷酸化，根据阿德尔斯坦等人（1978年）的研究，这可能导致肌球蛋白轻链的净去磷酸化，并伴随收缩反应的抑制。
