DOWN-REGULATION OF IMIDAZOLINE SITES IN RABBIT KIDNEY

The effects of 6 days treatment with guanabenz, clonidine, rilmenidine and idazoxan on [H-3]idazoxan and [H-3]clonidine binding to imidazoli ne sites on rabbit kidney membranes were compared. Guanabenz and rilme nidine treatment resulted in a decrease in B(max) for [H-3]clonidine b inding and guanabenz treatment for [H-3]idazoxan binding consistent wi th the compounds in vitro affinities for the imidazoline binding sites . [H-3]Idazoxan binding was also decreased by idazoxan treatment sugge sting that idazoxan may act as an agonist at this site. These results show that imidazoline sites in kidney may be modified during chronic d rug treatment and provide further evidence for differences between the sites labelled by the two ligands.