Simon M F, Chap H, Douste-Blazy L
FEBS Lett. 1984 May 7;170(1):43-8. doi: 10.1016/0014-5793(84)81365-4.
Human platelets loaded with the fluorescent Ca2+ indicator quin2 and with different radioactive compounds including [3H]serotonin, [14C]arachidonic acid (AA) and [32P]orthophosphate were stimulated by thrombin under conditions producing secretion. In the absence of external Ca2+ (Ca2+e), cytoplasmic free [Ca2+], [Ca2+]i, increased to 340 nM, against 1685 nM at 1 mM [Ca2+]e. In both cases, diglyceride and phosphatidic acid production proceeded at the same rate, whereas AA release was inhibited at low [Ca2+]i. It is concluded that, at variance with phospholipase A2, phospholipase C activation does not depend on [Ca2+]i. These results give further support to the hypothesis of a Ca2+-independent pathway of cell activation involving phospholipase C and protein kinase C.
用荧光Ca2+指示剂喹啉2以及包括[3H]5-羟色胺、[14C]花生四烯酸（AA）和[32P]正磷酸盐在内的不同放射性化合物加载的人血小板，在产生分泌的条件下用凝血酶刺激。在没有细胞外Ca2+（Ca2+e）的情况下，细胞质游离Ca2+，即[Ca2+]i，增加到340 nM，而在1 mM [Ca2+]e时为1685 nM。在这两种情况下，甘油二酯和磷脂酸的产生速率相同，而在低[Ca2+]i时AA释放受到抑制。得出的结论是，与磷脂酶A2不同，磷脂酶C的激活不依赖于[Ca2+]i。这些结果进一步支持了涉及磷脂酶C和蛋白激酶C的细胞激活的Ca2+非依赖性途径的假说。
