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Activation of phospholipase C in thrombin-stimulated platelets does not depend on cytoplasmic free calcium concentration

Authors
Publisher
Elsevier B.V.
Publication Date
Volume
170
Issue
1
Identifiers
DOI: 10.1016/0014-5793(84)81365-4
Keywords
  • Platelet Activation
  • Thrombin
  • Phospholipase C
  • Inositol Phospholipid
  • Calcium
  • Fluorescent Indicator
Disciplines
  • Biology

Abstract

Abstract Human platelets loaded with the fluorescent Ca 2+ 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 Ca 2+ (Ca 2+ e), cytoplasmic free [Ca 2+], [Ca 2+] i, increased to 340 nM, against 1685 nM at 1 mM [Ca 2+] e. In both cases, diglyceride and phosphatidic acid production proceeded at the same rate, whereas AA release was inhibited at low [Ca 2+] i. It is concluded that, at variance with phospholipase A 2, phospholipase C activation does not depend on [Ca 2+] i. These results give further support to the hypothesis of a Ca 2+-independent pathway of cell activation involving phospholipase C and protein kinase C.

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