Interactions between soluble placental opioid receptors and lectins

The final concentration of l% of digitonin and MgS04 5 mmol/L were added to human placental P2. After solubilization and absorption of excess detergent the supernatant was referred to be the digitonin/MgS04 solubilized placental opioid receptors. The KD and Bmax of [3H]etorphine binding to this preparation was 6.62 nmol/L and 54.1 pmol/g protein respectively. The IC50 of selected ligands for [3H]etorphine to this preparation showed that the binding characteristics of this preparation were more similar to the kappa subtype opioid receptors of brain and other tissues. The results in studying sugar affinity between 5 lectins and the soluble placental opioid receptors by precipitation method and/or column method showed that only wheat germ agglutinin could bind soluble placental opioid receptors with sugar affinity. After passing WGA-agarose column, the placental opioid receptors were enriched by about 10 folds.