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May 1, 1982Hypertension

Calcium- and endothelial-mediated vascular smooth muscle relaxation in rabbit aorta.

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Authors

HSHarold A. SingerMPM J Peach

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Overview

Experimental study demonstrates calcium-dependent endothelial relaxation in rabbit aortic tissue, indicating that extracellular calcium drives the production or release of relaxing factors.

Key Points

  • To determine the role of extracellular calcium and an intact endothelium in vascular smooth muscle relaxation induced by methacholine and A23187 in rabbit aorta.
  • Examined phenylephrine-contracted rabbit aortic rings with either intact or mechanically disrupted endothelium, verified by transmission and scanning electron microscopy.
  • Tested dose-dependent relaxation responses to methacholine (10⁻⁸ to 10⁻⁶ M) and calcium ionophore A23187 (10⁻⁸ to 10⁻⁶ M).
  • Assessed relaxation following calcium removal from the incubation medium and treatment with calcium-channel blockers verapamil (10 μM) and nifedipine (0.5 μM).
  • Endothelial removal abolished relaxation, causing methacholine to induce dose-dependent contractions at concentrations above 10⁻⁷ M.
  • Deletion of extracellular calcium inhibited maximum methacholine-induced relaxation by 67% and A23187-induced relaxation by 92%.
  • Verapamil and nifedipine inhibited maximum methacholine relaxations by 39% and 45%, and A23187 relaxations by 43% and 47%, without shifting the ED50 for methacholine (2.5 x 10⁻⁷ M) or A23187 (6 x 10⁻⁸ M).

Cite This Study

Singer et al. (1982) studied this question.

synapsesocial.com/papers/6a6f13c3fe4101aa97dfaeebhttps://doi.org/10.1161/01.hyp.4.3_pt_2.19
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