Vickers J D, Kinlough-Rathbone R L, Mustard J F
Biochem J. 1986 Jul 15;237(2):327-32. doi: 10.1042/bj2370327.
Addition of 10 micron-ADP to washed rabbit platelets caused platelet shape change and aggregation without release of the contents of the amine-storage granules, and caused a transient decrease (8.8% at 10 s) in the amount of phosphatidylinositol 4,5-bisphosphate (PIP2). By 20 s the decrease in PIP2 was no longer apparent, but by 60 s the amount of PIP2 was again decreased. Addition of thrombin (1 unit/ml), which causes platelet shape change, aggregation and the release of the contents of the amine-storage granules, caused a decrease in the amount of PIP2 (8.0% at 10 s); at 60 s the amount of PIP2 was not significantly different from that in controls. In platelets prelabelled with [3H]glycerol, the specific radioactivity of PIP2 was increased at 10 s in ADP-stimulated platelets, and unchanged in thrombin-stimulated platelets. In platelets prelabelled with [3H]inositol and incubated with 20 mM-Li+ to inhibit the degradation of the inositol phosphates to inositol, there was no increase in the labelling of inositol trisphosphate (IP3) upon stimulation with ADP. In contrast, stimulation with thrombin caused a significant increase in the labelling of IP3 at 10 s. These differences in the changes in polyphosphoinositide metabolism in ADP- and thrombin-stimulated platelets are consistent with the hypothesis that the decrease in PIP2 in ADP-stimulated platelets may be due not to degradation of PIP2 by phospholipase C, but rather to a shift in the equilibrium between PIP2 and phosphatidylinositol 4-phosphate (PIP). Increases in the labelling of phosphatidic acid at 10 s and of inositol bisphosphate and inositol phosphate after 20 s are consistent with phospholipase C being stimulated through some other mechanism that leads to the degradation of PIP and phosphatidylinositol; one possibility is that ADP causes an increase in cytoplasmic Ca2+.
向洗涤过的兔血小板中添加10微米的二磷酸腺苷（ADP）会导致血小板形状改变和聚集，但胺储存颗粒内容物不释放，同时会使磷脂酰肌醇4,5 - 二磷酸（PIP2）的量短暂减少（10秒时减少8.8%）。到20秒时，PIP2的减少不再明显，但到60秒时，PIP2的量再次减少。添加凝血酶（1单位/毫升），它会导致血小板形状改变、聚集以及胺储存颗粒内容物的释放，会使PIP2的量减少（10秒时减少8.0%）；在60秒时，PIP2的量与对照组相比无显著差异。在用[3H]甘油预标记的血小板中，ADP刺激的血小板在10秒时PIP2的比放射性增加，而凝血酶刺激的血小板中则无变化。在用[3H]肌醇预标记并与20毫摩尔/升锂离子一起孵育以抑制肌醇磷酸降解为肌醇的血小板中，ADP刺激后肌醇三磷酸（IP3）的标记没有增加。相比之下，凝血酶刺激在10秒时导致IP3的标记显著增加。ADP和凝血酶刺激的血小板中多磷酸肌醇代谢变化的这些差异与以下假设一致，即ADP刺激的血小板中PIP2的减少可能不是由于磷脂酶C对PIP2的降解，而是由于PIP2与磷脂酰肌醇4 - 磷酸（PIP）之间平衡的改变。10秒时磷脂酸标记的增加以及20秒后肌醇二磷酸和肌醇磷酸标记的增加与磷脂酶C通过某种其他机制被刺激导致PIP和磷脂酰肌醇降解一致；一种可能性是ADP导致细胞质钙离子浓度增加。
