O'Rourke F A, Halenda S P, Zavoico G B, Feinstein M B
J Biol Chem. 1985 Jan 25;260(2):956-62.
Human platelet membrane vesicles that accumulated Ca2+ in the presence of ATP were isolated on an isoosmotic KCl-Percoll gradient. ATP-dependent Ca2+ uptake was stimulated by oxalate and phosphate to steady-state levels of greater than 100 nmol/mg protein, and the accumulated Ca2+ could be largely released by ionophore A23187. Inositol 1,4,5-trisphosphate, in a dose-dependent manner (0.5-5.0 microM), caused the rapid release (less than 5 s) of 40-70% of the total A23187-releasable store of accumulated Ca2+. The membrane vesicles that release accumulated Ca2+ in response to inositol 1,4,5-trisphosphate were enriched in enzymes characteristically found in smooth endoplasmic reticulum. These results support the hypothesis that inositol 1,4,5-trisphosphate, produced by the hydrolysis of phosphatidylinositol 1,4-bisphosphate in response to stimulation of cell surface receptors, is a second messenger mediating the release of Ca2+ from intracellular storage sites.
在ATP存在的情况下积累了Ca2+的人血小板膜囊泡，通过等渗KCl- Percoll梯度进行分离。草酸盐和磷酸盐可刺激ATP依赖的Ca2+摄取，使其达到大于100 nmol/mg蛋白质的稳态水平，并且积累的Ca2+可被离子载体A23187大量释放。肌醇1,4,5-三磷酸以剂量依赖方式（0.5 - 5.0 microM）导致积累的Ca2+总量中40 - 70%的快速释放（小于5秒）。响应肌醇1,4,5-三磷酸而释放积累的Ca2+的膜囊泡富含在滑面内质网中典型存在的酶。这些结果支持这样的假说：响应细胞表面受体刺激，由磷脂酰肌醇1,4-二磷酸水解产生的肌醇1,4,5-三磷酸是介导Ca2+从细胞内储存位点释放的第二信使。
