Acidosis-induced protein tyrosine phosphorylation depends on Ca 2+ influx via voltage-dependent Ca2+ channels in SHR aorta

Dileep Kumar Rohra, Tohru Yamakuni, Yasushi Ohizumi

Research output: Contribution to journalArticle

Abstract

The contractile response to acidosis in isolated aorta from spontaneously hypertensive rat (SHR) depends upon tyrosine phosphorylation of phosphatidylinositol 3 kinase (PI3-kinase) and Ca2+ influx via voltage-dependent Ca2+ channels (VDCC). In this study, verapamil, a VDCC inhibitor, was shown to markedly inhibit acidic pH-induced contraction, whereas the residual contraction in the presence of verapamil was unaffected by the PI3-kinase inhibitor, 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one hydrochloride (LY-294002). Interestingly, the LY-294002-insensitive component of contraction was further inhibited by verapamil in the presence of LY-294002. Western blotting revealed that acidosis stimulated tyrosine phosphorylation of p85, which was abolished when tissues were pretreated with tyrphostin 23, a tyrosine kinase inhibitor, verapamil or EGTA. In fura-2-loaded aortic strips, acidosis induced a rise in intracellular Ca2+ ([Ca2+] i) that was partially inhibited by LY-294002. The residual increase in [Ca2+]i caused by acidosis in the presence of LY-294002 was abolished by verapamil. These findings suggest that acidosis-induced Ca2+ influx through VDCC is the upstream event leading to the tyrosine phosphorylation of PI3-kinase, which in turn contributes to the enhancement of Ca2+ entry to some extent in SHR aorta.

Original languageEnglish
Pages (from-to)105-111
Number of pages7
JournalEuropean Journal of Pharmacology
Volume504
Issue number1-2
DOIs
Publication statusPublished - 2004 Nov 3

Keywords

  • Acidosis
  • Aorta
  • Phosphatidylinositol 3 kinase
  • Spontaneously hypertensive
  • Tyrosine phosphorylation
  • Voltage-dependent calcium channel
  • rat

ASJC Scopus subject areas

  • Pharmacology

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