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Haptoglobin transport into human ovarian follicles and its binding to apolipoprotein A-1

Published online by Cambridge University Press:  05 April 2001

A. Porta
Affiliation:
International Institute of Genetics and Biophysics - CNR, via G. Marconi 10, 80125 Naples, Italy
E. Cassano
Affiliation:
International Institute of Genetics and Biophysics - CNR, via G. Marconi 10, 80125 Naples, Italy
M. Balestrieri
Affiliation:
Dipartimento di Fisiologia Generale ed Ambientale, Università di Napoli Federico II, via Mezzocannone 8, 80134 Naples, Italy
M. Bianco
Affiliation:
Diagnostica Medica, via Nazionale 146, 83010 Torrette di Mercogliano (Avellino), Italy
R. Picone
Affiliation:
Diagnostica Medica, via Nazionale 146, 83010 Torrette di Mercogliano (Avellino), Italy
C. De Stefano
Affiliation:
Diagnostica Medica, via Nazionale 146, 83010 Torrette di Mercogliano (Avellino), Italy
P. Abrescia
Affiliation:
International Institute of Genetics and Biophysics - CNR, via G. Marconi 10, 80125 Naples, Italy Dipartimento di Fisiologia Generale ed Ambientale, Università di Napoli Federico II, via Mezzocannone 8, 80134 Naples, Italy

Abstract

Controlled ovarian stimulation was induced in 19 women for in vitro fertilisation/embryo transfer. After ovum pick-up, haptoglobin titres 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 as 92%, 73% and 57% of the blood level of 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 of 49 and 3 of 49 fertilised oocytes, respectively. Complexes of haptoglobin with apolipoprotein A-1 were isolated from follicular fluids by affinity chromatography with haemoglobin. The haptoglobin β chain, after Western blotting and incubation with apolipoprotein A-1, was found to be involved in the protein–protein interaction as detected by anti-apolipoprotein A-1 antibodies. Complexes from separate fluids were analysed by electrophoresis and densitometry: the plain β chain/apolipoprotein A-1 stoichiometric ratio was 0.75 and 1.40 in fluids associated with fertilised and unfertilised oocytes respectively. The results suggest that haptoglobin transport in the follicle depends on the integrity of the blood–follicle barrier and might be associated with oocyte quality, possibly by interfering with the role of apoliprotein A-1 in cholesterol or vitamin E exchange between high-density lipoproteins and granulosa cells.

Type
Research Article
Copyright
1999 Cambridge University Press

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