The effect of seminal plasma on human sperm-zona pellucida binding

The aim of this study was to determine the effect of different concentrations of seminal plasma (SP) in insemination medium on human sperm-zona pellucida (ZP) binding. The effects of fresh SP [50% (n = 10) and 1% (n = 9)], frozen-thawed versus fresh SP [5% (n = 10)] and frozen-thawed SP [5% (n = 10) and 1% (n = 9)] on sperm-ZP binding were examined using hemizona assays. The validity of the hemizona assay as performed in this study was also examined. Relative sperm binding percentages were determined for respective hemizonae, and the hemizona index was calculated for each experimental group and compared statistically. The 50% native SP inhibited sperm-ZP binding by approximately 70% (P = 0.0051), while 1% native SP enhanced sperm-ZP binding by approximately 350% (P = 0.0051). Significantly more spermatozoa (mean +/- SD, 172.00 +/- 54.12) bound to zonae in the presence of 5% frozen-thawed SP than with 5% SP that had not been frozen (mean +/- SD, 127.00 +/- 69.18; P = 0.0431). The 1 and 5% frozen-thawed SP stimulated sperm-ZP binding by approximately 400 and approximately 250% respectively (P = 0.0077 and 0.0051 respectively). It is concluded that SP concentrations found in insemination media during assisted reproductive techniques do not inhibit but in fact enhance sperm-ZP binding.