Haptoglobin transport into human ovarian follicles and its binding to the apoliprotein A-1.

Controlled ovarian stimulation was induced in 19 women for IVF-ET. After ovum pick up, Haptoglobin titers were determined by ELISA in sera and homologous follicular fluids. The Haptoglobin phenotype of each subject was assessed and the penetration of the protein forms through the blood-follicle barrier was predicted on the basis of their molecular weight. The penetration threshold compatible with the barrier integrity was calculated 92, 73 and 57% of the blood level for phenotypes Hpt 1-1, Hpt 1-2 and Hpt 2-2 respectively. Penetration values comparable-lower or higher than threshold were found associated with 46/49 or 3/49 fertilized oocytes respectively. Complexes of Haptoglobin with Apoliprotein A-1 were isolated from follicular fluids by affinity chromatography with Hemoglobin. The Haptoglobin beta chain, after Western blotting and incubation with Apolipoprotein A-1, was found involved in the protein-protein interaction as detected by anti-Apoliprotein A-1 antibodies. Complexes from separate fluids were analysed by electrophoresis and densitometry : the beta chain/Apoliprotein A-1 stoichiometric ratio was found 0.75 and 1.40 in fluids associated with fertilized and unfertilised oocytes respectively. The results suggest that the Haptoglobin transport in the follicle depends on the integrity of the blood-follicle and might be associated with the oocyte quality, possibly by interfering with the role of Apoliprotein A-1 in cholesterol or vitamin E exchange between HDLs and granulosa cells.