Contrasting effects of hypoxia on tension in rat pulmonary and mesenteric arteries

X. J. Yuan, M. L. Tod, L. J. Rubin, M. P. Blaustein

Research output: Contribution to journalArticle

117 Scopus citations

Abstract

The effects of hypoxia on resting and K-stimulated tension were tested on small rings of rat pulmonary and mesenteric resistance arteries (SPA and SMA, respectively) and on the large branches of the main pulmonary artery (LPA). Reduction of PO2 from ~135 Torr to <40 Torr slowly increased SPA and LPA resting tension but did not affect SMA tension. The increases in SPA and LPA tension during hypoxia were reversible and were dependent on external Ca2+. Verapamil, 10-6 M, inhibited the hypoxic pulmonary vasoconstriction by 53-78%. The hypoxia-contracted SPA and LPA were relaxed by 2-4 μM cromakalim; these relaxations were reversed by 2 μM glibenclamide. Hypoxia attenuated the K-stimulated tension (ΔT(K)) in both SPA and SMA at all external K+ concentrations ([K+](o) = 10-100 mM) without affecting the shapes of the respective [K+](o)-tension curves. However, the SPA curve was located much farther to the left on the [K+](o) axis than the SMA curve. [K+](o) ~13 mM evoked half-maximal increase in SPA tension; maximal ΔT(K) was observed at [K+](o) ≥ 30 mM. In contrast, [K+](o) <20 mM induced a negligible increase in SMA tension, whereas 35-40 mM K+ activated about one-half of the increase in tension elicited by 100 mM K+. The LPA [K+](o)-tension curve in normoxia was intermediate between the SMA and SPA curves, but hypoxia shifted the LPA curve to the left: ΔT(K) was augmented at [K+](o) <20 mM and attenuated at high [K+](o). Removal of the endothelium in LPA did not prevent hypoxia-induced increases in tension. Indeed, there was a significantly greater contraction to hypoxia in LPA without endothelium compared with LPA with an intact endothelium. Our data support the hypothesis that hypoxia-induced pulmonary vasoconstriction is the result of direct membrane depolarization and/or modulation of the voltage sensitivity of Ca2+ channels in the sarcolemma.

Original languageEnglish (US)
Pages (from-to)H281-H89
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume259
Issue number2 28-2
StatePublished - Jan 1 1990
Externally publishedYes

Keywords

  • cromakalim
  • endothelium
  • glibenclamide
  • hypoxic pulmonary vasoconstriction
  • verapamil

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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