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      Mechanisms by Which Smooth Muscle Sensitivity May Be Altered by Calcium

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          6-Hydroxydopamine (6-OHDA) increased the sensitivity of rat, rabbit and guinea pig portal veins to norepinephrine (NE), methoxamine (ME), barium (Ba<sup>++</sup>) and calcium (Ca<sup>++</sup>) but not to potassium (K<sup>+</sup>). Reserpine potentiated the responses of NE, ME and Ca<sup>++</sup> but not Ba<sup>++</sup> or K<sup>+</sup> in rabbit and guinea pig veins and did not alter the sensitivity of rat veins to all agonists tested. Cocaine only potentiated the NE responses of the veins and decreased the sensitivity of rabbit and guinea pig veins to K<sup>+</sup>. 6-OHDA increased <sup>45</sup>Ca-influx in all veins whereas reserpine increased <sup>45</sup>Ca -influx only in rabbit and guinea pig veins. Cocaine failed to increase <sup>45</sup>Ca-influx in all veins tested. NE, ME and K<sup>+</sup> increased <sup>45</sup>Ca-influx in the veins from the different animals. The agonist-induced <sup>45</sup>Ca-influx was greater in most of the supersensitive veins than in the control veins. In veins that failed to develop supersensitivity, agonist-induced <sup>45</sup>Ca-influx did not differ from that of the control veins. It is concluded that the development of super- and subsensitivity exhibits species variation and that the alteration in Ca<sup>++</sup> influx would be consistent with the changes in sensitivity of the venous smooth muscle.

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          Author and article information

          J Vasc Res
          Journal of Vascular Research
          S. Karger AG
          18 September 2008
          : 15
          : 1-3
          : 93-109
          University of Hawaii, Department of Pharmacology, School of Medicine, Biomedical Sciences Bldg., Honolulu, Hawaii
          158156 Blood Vessels 1978;15:93–109
          © 1978 S. Karger AG, Basel

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          Page count
          Pages: 17
          Molecular and Cellular Aspects of Vascular Smooth Muscle in Health and Disease


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