Effect of pertussis toxin on α 2-adrenoceptors: decreased formation of the high-affinity state for agonists

Administration of pertussis toxin to hamsters abolishes the α 2-adrenergic inhibition of adenylate cyclase in their adipocytes. The toxin did not modify the number of adipocyte α 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.