1. A liver canalicular plasma-membrane fraction enriched 115-155-fold in five marker enzymes relative to the tissue homogenate was obtained by sonication of liver plasma membranes followed by fractionation in iso-osmotic Nycodenz gradients. 2. Two lateral-plasma membrane fractions were also collected by this procedure; the lighter-density fraction was still associated with canalicular membranes...

The characterization of pharmacological receptors in subcellular preparations has, to date, relied mainly on observations of the binding properties of radioactively labelled ligands. Minimal criteria for receptor-specific binding are that a component of binding should saturate with increasing concentrations of the ligand and that only drugs with the appropriate pharmacological specificity, and ...