Effect of Phospholipase C Induced Hydrolysis of Phospholipids on Membrane-Bound and Water-Soluble LH/hCG Receptors in Porcine Corpora Lutea

Summary

The role of phospholipids in the function of LH/hCG receptors was studied in two receptor preparations: the membrane fraction of porcine corpora lutea (CL) and the water-soluble receptor in follicular fluid (LFF) which was characterized. Digestion of CL membranes with phospholipase C (PL-C) abolished, in a dose responsive manner, specific binding of [¹²⁵I]hCG and decreased phospholipid concentrations in the membranes. This loss of LH/hCG receptors was prevented by o-phenanthroline, an inhibitor of PL-C. A similar effect on membrane-bound receptors was observed when lipids were extracted with ethanol-diethylether. On the other hand, treatment of water-soluble receptors with PL-C or delipidation of LFF with Amberlit IRA 400 had no effect on [¹²⁵I]hCG specific binding. These data suggest that phospolipids play an important role in the accessibility of membrane-bound receptors but are not involved in direct interaction of gonadotropin with binding sites.

Key words

Phospholipase C - Phospholipids - LH/hCG Receptors