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      Uptake and O-Methylation of Isoprenaline in the Rabbit Ear Artery

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          Factors which influence uptake and O-methylation of <sup>3</sup>Hisoprenaline (<sup>3</sup>HISO) by isolated segments of the rabbit ear artery were investigated. The tendency of the artery to accumulate unchanged amine was enhanced either when the O-methylation of ISO approached saturation at a high substrate concentration (6 µmol l<sup>–1</sup> ISO), or when O-methylation was inhibited. Under these conditions, deoxycorticosterone acetate (DOCA) partially inhibited the accumulation of ISO. DOCA exerted a stronger inhibitory effect on O-methylation, but only at low ISO concentrations (0.2 and 0.8 µmol l<sup>–1</sup>). The results are interpreted as evidence that (a) O-methylation in the intact artery is a saturable process which serves to limit the accumulation of <sup>3</sup>HISO when the bathing concentration of the amine is low, and (b) DOCA exerts its effects by inhibiting extraneuronal uptake into the compartment possessing O-methylating activity. Analysis of the kinetics of efflux of <sup>3</sup>HISO suggested that O-methylation was restricted to only one compartment, whereas unchanged ISO was accumulated within at least two compartments in addition to the extracellular compartment. Attention is drawn to a small but significant inhibitory effect of chronic sympathetic denervation on the accumulation, although not the O-methylation of ISO, raising the possibility that there may also be distribution of <sup>3</sup>HISO within the sympathetic nerves.

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          Author and article information

          J Vasc Res
          Journal of Vascular Research
          S. Karger AG
          19 September 2008
          : 17
          : 5
          : 229-245
          Department of Human Physiology and Pharmacology, University of Adelaide, Adelaide, S.A.
          158253 Blood Vessels 1980;17:229–245
          © 1980 S. Karger AG, Basel

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          Pages: 17
          Research Paper


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