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      Role of Calcium in Different Layers of Vascular Smooth Muscle in Norepinephrine Contraction

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          The role of calcium present in adventitial and media-intimal layers of rabbit aorta in the fast (F-) and the slow (S-) components of norepinephrine (10<sup>-5</sup>m) contraction was evaluated in this study. An increased sensitivity and decreased maximum tension to response to norepinephrine was observed in adventitia-free aorta as compared to whole aorta. Incubation in calcium-free Ringer solution with or without EDTA decreased the F-component of norepinephrine contraction of the adventitia-free aorta, whereas the F-component of the whole aorta was not affected. The S-component of both preparations was abolished in calcium-free Ringer solution. Norepinephrine increased calcium uptake into whole and adventitia-free aortic strips. An increase in calcium uptake induced by norepinephrine during the F-component of norepinephrine contraction was also observed. <sup>45</sup>Ca efflux studies revealed the presence of an exchangeable calcium fraction in the adventitial layer. These data suggest that the F-component of norepinephrine contraction is partially dependent on the extracellular calcium distributed in the adventitial layer of rabbit aorta.

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          Author and article information

          J Vasc Res
          Journal of Vascular Research
          S. Karger AG
          18 September 2008
          : 13
          : 4
          : 193-209
          Department of Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, Tex.
          158089 Blood Vessels 1976;13:193–209
          © 1976 S. Karger AG, Basel

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          Pages: 17
          Research Paper


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