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 imidazoline sites on rabbit kidney membranes were compared. Guanabenz and rilmenidine treatment resulted in a decrease in B(max) for [H-3]clonidine binding and guanabenz treatment for [H-3]idazoxan binding consistent with the compounds in vitro affinities for the imidazoline binding sites. [H-3]Idazoxan binding was also decreased by idazoxan treatment suggesting that idazoxan may act as an agonist at this site. These results show that imidazoline sites in kidney may be modified during chronic drug treatment and provide further evidence for differences between the sites labelled by the two ligands.