The influence of sera, follicular fluids and seminal plasma on human sperm-zona pellucida binding

The purpose of this study was to assess the influence of male, female and fetal cord sera, follicular fluid, and seminal plasma on human sperm-zona pellucida binding, using the hemizona assay. Steroids, gonadotrophins, growth hormone and prolactin concentrations in follicular fluid and sera were also analysed. The influence of follicular fluid (10 or 50%, v/v) and sera (10%) on sperm-zona pellucida binding was investigated by supplementing the sperm processing medium as well as the sperm-hemizona incubation medium. Different seminal plasma concentrations (1 or 10%) were added to the sperm-hemizona incubation medium. Supplementation with 10% day 3 donor serum was used as a control throughout experimentation. Although supplementation with male sera and fetal cord serum exerted a stimulatory effect (36 and 90% respectively; P < 0.029) on sperm-zona pellucida binding, hemizona indices obtained with addition of male sera, fetal cord serum and sera obtained from sub-fertile in-vitro fertilization (IVF) patients on day 12 of their menstrual cycle did not differ significantly (P > 0.05). Final progesterone concentrations in sperm-zona pellucida incubation media (10% follicular fluid supplementation), which ranged from 0.788 to 3.85 microg/ml, enhanced sperm binding to the zonae by >100% (P < 0.02). The utilization of follicular fluid (10%) as a natural physiological stimulus to enhance sperm-zona pellucida binding in an IVF setting is recommended. The presence of seminal plasma in the spermzona pellucida incubation media showed no beneficial effect on the binding ability of sperm, and can be viewed as an unfavourable substance in the proximity of the oocyte.