Yoo S H, Albanesi J P
Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas 75235-9041.
J Biol Chem. 1990 Aug 15;265(23):13446-8.
The effect of inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) and calcium ionophore A23187 on Ca2+ release from bovine adrenal medullary secretory vesicles and microsomes was examined. Ins(1,4,5)P3 released 3.5 nmol of Ca2+/mg protein from secretory vesicles and 1.5 nmol of Ca2+/mg protein from microsomes as measured by a Ca2(+)-selective electrode. However, A23187 promoted Ca2+ uptake into vesicles while releasing Ca2+ from microsomes. Ins(1,4,5)P3-induced Ca2+ release from secretory vesicles was rapid, but the released Ca2+ was absorbed within 3 min during which the Ins(1,4,5)P3-releasable pools were refilled. The in situ calcium content of secretory vesicle measured by atomic absorption spectrometry was 112 +/- 6.3 nmol/mg protein indicating the potential importance of secretory vesicles as an intracellular Ca2+ store. The high Ca2(+)-buffering capacity of secretory vesicles is presumed to be due to the high Ca2(+)-binding capacity of chromogranin A, the major intravesicular protein, which has calsequestrin-like properties.
研究了肌醇 1,4,5 - 三磷酸（Ins(1,4,5)P3）和钙离子载体 A23187 对牛肾上腺髓质分泌囊泡和微粒体中 Ca2+ 释放的影响。通过 Ca2+ 选择性电极测量，Ins(1,4,5)P3 从分泌囊泡中释放出 3.5 nmol Ca2+/mg 蛋白质，从微粒体中释放出 1.5 nmol Ca2+/mg 蛋白质。然而，A23187 促进 Ca2+ 摄入囊泡，同时从微粒体中释放 Ca2+。Ins(1,4,5)P3 诱导的分泌囊泡 Ca2+ 释放迅速，但释放的 Ca2+ 在 3 分钟内被吸收，在此期间 Ins(1,4,5)P3 可释放池被重新填充。通过原子吸收光谱法测量，分泌囊泡的原位钙含量为 112±6.3 nmol/mg 蛋白质，表明分泌囊泡作为细胞内 Ca2+ 储存库的潜在重要性。推测分泌囊泡的高 Ca2+ 缓冲能力是由于主要的囊泡内蛋白质嗜铬粒蛋白 A 的高 Ca2+ 结合能力，其具有类似钙网蛋白的特性。
