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

• Published in: Biology of reproduction 1997-09, Vol.57 (3), p.539-546
• Main Authors: GAMZU, R, YOGEV, L, PAZ, G, YAVETZ, H, LICHTENBERG, D
• Format: Article
• Language: English
• Subjects: Acrosome - drug effects; Acrosome - physiology; Biological and medical sciences; Birth control; Cholesterol - metabolism; Culture Media; Female; Gynecology. Andrology. Obstetrics; Humans; In Vitro Techniques; Liposomes; Male; Medical sciences; Phosphatidylcholines - pharmacology; Phospholipids - metabolism; Sperm Motility - drug effects; Sperm-Ovum Interactions - drug effects; Sperm-Ovum Interactions - physiology; Spermatozoa - drug effects; Spermatozoa - metabolism; Sterility. Assisted procreation; Zona Pellucida - metabolism
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod57.3.539

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.