Bromberg M E, Sevy R W, Daniel J L, Salganicoff L
Am J Physiol. 1985 Sep;249(3 Pt 1):C297-303. doi: 10.1152/ajpcell.1985.249.3.C297.
The relationship between tension and myosin 20,000-Da light chain phosphorylation in intact nonmuscle cells was investigated using a preparation of thrombin-activated, irreversibly aggregated platelets known as the platelet strip. Steady-state levels of tension generated by the platelet strip were found to be linearly related to the level of myosin phosphorylation. This relationship was observed during dose-dependent relaxation induced by the adenylate cyclase activators prostaglandin (PG) E1 and PGI2, and during contraction induced by ADP, epinephrine, and the prostaglandin endoperoxide analogue U-46619, which did not appreciably alter the basal level of adenosine 3',5'-cyclic monophosphate in the preparation. The fully relaxed platelet strip, in the absence of external Ca2+, was associated with a level of 12% light chain phosphorylation, which increased to 72% on maximal contraction. During both relaxation and contraction, changes in myosin phosphorylation were also found to precede or coincide with tension changes. Furthermore, steady-state contraction induced by ADP was associated with a maintained elevation in the level of myosin phosphorylation. These results support the concept that myosin phosphorylation is an important regulatory mechanism for contractility in platelets.
利用一种被称为血小板条的凝血酶激活、不可逆聚集的血小板制剂，研究了完整非肌肉细胞中张力与肌球蛋白20,000道尔顿轻链磷酸化之间的关系。发现血小板条产生的稳态张力水平与肌球蛋白磷酸化水平呈线性相关。在由腺苷酸环化酶激活剂前列腺素（PG）E1和PGI2诱导的剂量依赖性舒张过程中，以及在由ADP、肾上腺素和前列腺素内过氧化物类似物U-46619诱导的收缩过程中都观察到了这种关系，这些物质并没有明显改变制剂中3',5'-环磷酸腺苷的基础水平。在没有外部Ca2+的情况下，完全松弛的血小板条与12%的轻链磷酸化水平相关，在最大收缩时增加到72%。在舒张和收缩过程中，还发现肌球蛋白磷酸化的变化先于或与张力变化同时发生。此外，由ADP诱导的稳态收缩与肌球蛋白磷酸化水平的持续升高有关。这些结果支持了肌球蛋白磷酸化是血小板收缩性的重要调节机制这一概念。
