Agonist-evoked alkaline shift in the cytosolic pH set point for activation of Na+/H+ antiport in human platelets. The role of cytosolic Ca2+ and protein kinase C

M. Kimura, J. P. Gardner, A. Aviv

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Abstract

This work examines the roles of elevated cytosolic Ca2+ and stimulation of protein kinase C in agonist and non-agonist-mediated alkaline shift of the cytosolic pH set point for activation of Na+/H+ antiport in human platelets. Ca2+-depleted and control platelets were subjected to phorbol 12-myristate 13-acetate, thrombin, vasopressin, and ionomycin in 1 mM or Ca2+ free, nominally bicarbonate free media. To measure the cytosolic pH set point for Na+/H+ antiport activation, cells were acidified to different levels using the sodium propionate method. In some experiments protein kinase C was inhibited by staurosporine. Both protein kinase C stimulation and elevation of cytosolic Ca2+ can produce an alkaline shift in the pH set point for activation of Na+/H+ antiport in human platelets. However, the effect of Ca2+(i) on the pH set point predominates that of protein kinase C stimulation. Cytosolic Ca2+ is a prerequisite for agonist-evoked alkaline shift in the cytosolic pH set point for activation of Na+/H+ antiport. The cytosolic Ca2+ level is also essential for maintaining the basal cytosolic pH. These findings underscore the central role of cytosolic Ca2+ under basal and stimulated states in regulating cytosolic pH of human platelets.

Original languageEnglish (US)
Pages (from-to)21068-21074
Number of pages7
JournalJournal of Biological Chemistry
Volume265
Issue number34
StatePublished - 1990

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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