Oscillatory contractions in tail arteries from genetically hypertensive rats

Fred S. Lamb, J. Hurley Myers, Michael N. Hamlin, R. Clinton Webb

Research output: Contribution to journalArticle

41 Scopus citations

Abstract

This study characterizes a cellular mechanism for oscillatory contractions induced by norepinephrine in vascular smooth muscle from spontaneously hypertensive stroke prone rats (SHRSP). Helically cut strips of tail arteries from SHRSP and normotensive Wistar-Kyoto rats (VVKY) were mounted in a muscle bath for measurement of isometric force generation. Norepinephrine-induced responses of arteries from SHRSP were characterized by fluctuations in contractile activity, whereas those in arteries from WKY remained constant with time. The magnitude of the oscillatory contractile activity (frequency × mean amplitude) varied directly with norepinephrine concentration (5.9 × 10-9 to 1.8 ×10-7 M). The oscillatory contractile activity varied inversely with the potassium concentration (3-20 mMj of the buffer solution and directly with the calcium concentration (0.1-5.0 mM) of the buffer solution. The oscillatory activity was converted to maintained contraction by barium (10-4 M), quinidine (3 × 10-6 M), sparteine (10-3 M), D-600 (10-7 M), and nifedipine (10-6 M). Tetraethylammonium and 3,4-diaminopyridine, inhibitors of voltage-dependent potassium channels, did not alter the oscillatory contractile activity induced by norepinephrine. These observations suggest that oscillatory contractile activity in tail arteries from SHRSP is caused by an abnormal variation in potassium efflux during stimulation with norepinephrine. The altered potassium efflux appears to be related to calcium entry, which is sensitive to inhibition by channel blockers. This altered membrane property may contribute to changes in vascular sensitivity in hypertension.

Original languageEnglish (US)
Pages (from-to)25-30
Number of pages6
JournalHypertension
Volume7
Issue number3
DOIs
StatePublished - 1985

Keywords

  • Calcium
  • Calcium channel blockers
  • Norepinephrine
  • Potassium
  • Quinidine
  • Sparteine

ASJC Scopus subject areas

  • Internal Medicine

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    Lamb, F. S., Hurley Myers, J., Hamlin, M. N., & Clinton Webb, R. (1985). Oscillatory contractions in tail arteries from genetically hypertensive rats. Hypertension, 7(3), 25-30. https://doi.org/10.1161/01.hyp.7.3_pt_2.i25