title: Reduction of sperm cholesterol:phospholipid ratio is a possible mechanism for enhancement of human sperm binding to the zona pellucida following incubation with phosphatidylcholine liposomes.
abstract: TEST (TES (N-tris[hydroxymethyl]methyl-2-aminoethanesulfonic acid) and Tris) yolk buffer (TYB) has recently been shown to improve the binding capacity of spermatozoa to zona pellucidae. The present study had two objectives: 1) to elucidate which component(s) of TYB dominates this effect and 2) to define the responsible mechanism. Sperm samples obtained from subfertile men were incubated for 2 h in either TYB or media containing egg yolk lipoproteins or phospholipids. After incubation, sperm binding was tested by the hemizona assay. Yolk lipoprotein-treated spermatozoa bound hemizonae with efficiency equal to that of the spermatozoa incubated in control medium. Conversely, incubation of spermatozoa in media containing either TYB, yolk-phospholipids, or pure phosphatidylcholine (PC) resulted in a 2- to 3-fold increased binding capacity (p < 0.01). A close correlation was found between the effect of yolk-phospholipids and TYB on the binding capacity of the same sperm samples, compared to spermatozoa incubated in control medium. Incubation of spermatozoa in yolk phospholipid medium caused a dose-dependent increase of sperm binding capacity (p < 0.05). Treatment of sperm samples with 1 mg/ml or more of purified PC preparation also resulted in a reduction of the sperm cholesterol:phospholipid molar ratio. Significant correlations between the effects of the treatments on sperm cholesterol: phospholipid molar ratio and sperm binding were obtained with yolk-phospholipids (r = -0.55) or 1 mg/ml purified PC (r = -0.61). We conclude that 1) the enhanced binding capacity of human spermatozoa following TYB treatment is probably due to yolk-phospholipids, mainly egg yolk PC; and 2) it appears that the enhanced binding capacity of human spermatozoa following treatment with egg yolk-containing media may be a result of the reduction of the cholesterol:phospholipid molar ratio in the sperm cells.
authors.affiliation: Institute for the Study of Fertility, Serlin Maternity Hospital, Tel Aviv, Israel.
authors.forename: R
authors.initials: R
authors.lastname: Gamzu
authors.forename: L
authors.initials: L
authors.lastname: Yogev
authors.forename: G
authors.initials: G
authors.lastname: Paz
authors.forename: H
authors.initials: H
authors.lastname: Yavetz
authors.forename: D
authors.initials: D
authors.lastname: Lichtenberg
mesh_terms: D000177:Acrosome / Q000187:drug effects / Q000502:physiology; D002784:Cholesterol / Q000378:metabolism*; D003470:Culture Media; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008081:Liposomes; D008297:Male; D010713:Phosphatidylcholines / Q000494:pharmacology; D010743:Phospholipids / Q000378:metabolism*; D013081:Sperm Motility / Q000187:drug effects; D013084:Sperm-Ovum Interactions / Q000187:drug effects / Q000502:physiology*; D013094:Spermatozoa / Q000187:drug effects / Q000378:metabolism*; D015044:Zona Pellucida / Q000378:metabolism*
chemical_list: D003470:Culture Media; D008081:Liposomes; D010713:Phosphatidylcholines; D010743:Phospholipids; D002784:Cholesterol