Effect of pertussis toxin on alpha 2-adrenoceptors: decreased formation of the high-affinity state for agonists.
Administration of pertussis toxin to hamsters abolishes the alpha 2-adrenergic inhibition of adenylate cyclase in their adipocytes. The toxin did not modify the number of adipocyte alpha 2-adrenoceptors or their affinity for antagonists. In contrast, the affinity for agonists was significantly diminished in adipocyte membranes obtained from pertussis toxin-treated hamsters as compared to the controls. This decrease in affinity was due to a significant diminution in the proportion of sites displaying the high-affinity state for agonists. It is concluded that pertussis toxin induces a shift in the proportion of sites in high- and low-affinity states. for agonists towards the low-affinity conformation.
García-Sáinz, JA; Boyer, JL; Michel, T; Sawyer, D; Stiles, GL; Dohlman, H; Lefkowitz, RJ
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