Multiple binding sites of [3H]clonidine on hepatic plasma membranes

The binding of [3H]clonidine on mouse liver plasma membrane was a rapid, saturable and reversible process. It was characterized by two types of population: high affinity receptors with KD of 6.76 +/- 1.02 nM and Bmax of 106.15 +/- 24.05 fmol/mg protein, and low affinity receptors with KD of 63.66 +/- 12.85 nM and Bmax of 818.06 +/- 128.49 fmol/mg protein. Displacement of [3H]clonidine from its binding sites by various ligands indicated that alpha 1--as well as alpha 2--adrenoceptors were involved in the high affinity system. The respective participation of these two types of receptors was discussed.