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      Effect of Ouabain and Alterations in Potassium Concentration on Relaxation Induced by Sodium Nitroprusside

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          Relaxation of the rat thoracic aorta induced by sodium nitroprusside, 8-bromo-cyclic GMP and cyclic nucleotide phosphodiesterase inhibitor M & B 22,948 was inhibited by exposure to K<sup>+</sup>-free solution and ouabain in a concentration-dependent manner. Relaxation occurring with the change in potassium concentration in media from 1 to 2 to 10 mM was increased by sodium nitroprusside, 8-bromo-cyclic GMP and M & B 22,948. Thus, agents and procedures known to decrease and increase the activity of the Na<sup>+</sup>, K<sup>+</sup>-pump, and presumably alter the membrane potential, inhibited and enhanced relaxation, respectively. Exposure to 1 mM K<sup>+</sup> solution increased the relaxation to low concentrations of sodium nitroprusside, but had no effect on relaxation induced by 8-bromo-cyclic GMP or M & B 22,948. Thus, another procedure which inhibits the Na<sup>+</sup>, K<sup>+</sup>-pump enhanced the effect of low concentrations of sodium nitroprusside on relaxation. Ouabain had no effect on sodium nitroprusside-induced accumulation of cyclic GMP. These results suggest that sodium nitroprusside may induce relaxation through cyclic GMP formation, effects on the Na<sup>+</sup>, K<sup>+</sup>-pump and/or hyper-polarization of the smooth muscle cell membrane.

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          Author and article information

          J Vasc Res
          Journal of Vascular Research
          S. Karger AG
          19 September 2008
          : 20
          : 5
          : 255-264
          Departments of Medicine and Pharmacology, Stanford University School of Medicine and Veterans Administration Medical Center, Palo Alto, Calif., USA
          158478 Blood Vessels 1983;20:255–264
          © 1983 S. Karger AG, Basel

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          Pages: 10
          Research Paper


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