Contribution of Na+/Ca2+ exchanger to the regulation of myogenic tone in isolated rat small arteries

S. Horiguchi, J. Watanabe, H. Kato, S. Baba, T. Shinozaki, M. Miura, M. Fukuchi, Y. Kagaya, K. Shirato

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6 Citations (Scopus)

Abstract

The contribution of the Na+/Ca2+ exchanger to the myogenic vascular tone was examined in rat isolated skeletal muscle small arteries (ASK) with pronounced myogenic tone and mesenteric small arteries (AMS) with little myogenic tone. Myogenic tone was assessed by the vascular inner diameter at transmural pressures of 40 and 100 mmHg. To depress the Na+/Ca2+ exchanger, the extracellular Na+ concentration ([Na+]o) was lowered from 143 to 1.2 mM by substituting choline-Cl for NaCl. The ASK developed significant myogenic tone and constricted further in low [Na+]o. Nifedipine (1 μM) reduced both myogenic tone and low [Na+]o-induced contraction. Because the membrane potential of ASK was not changed by low [Na+]o (-35 ± 2 mV at 143 mM [Na+]o,-37 ± 3 mV at 1.2 mM [Na+]o), depolarization-induced Ca2+ influx was not a cause of the low [Na+]o-induced contraction. The AMS did not develop significant myogenic tone. Although low [Na+]o also constricted AMS, the magnitude of constriction was significantly weaker than that in ASK (17 ± 4 vs. 47 ± 6%, P < 0.01, at 58 mM Na+). With Bay K 8644, AMS developed myogenic tone, and low [Na+]o-induced constriction was significantly increased. In conclusion, Na+/Ca2+ exchanger may play an important role in regulating myogenic tone, likely via mediating Ca2+-extrusion.

Original languageEnglish
Pages (from-to)167-173
Number of pages7
JournalActa Physiologica Scandinavica
Volume173
Issue number2
DOIs
Publication statusPublished - 2001

Keywords

  • Bay K 8644
  • Extracellular Na concentration
  • Membrane potential
  • Mesenteric small arteries
  • Myogenic tone
  • Nifedipine
  • Skeletal muscle small arteries
  • Voltage dependent Ca channels

ASJC Scopus subject areas

  • Physiology

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