Blocking of human fertilization by carbohydrates

The zona penetration test and triple stain technique were used to elucidate the blocking effects of carbohydrates on human fertilization and their mechanisms. In the presence of D-mannose or D-fructose (final concentration, 50 mmol/l), sperm penetration through the human zona pellucida was completely blocked. The triple stain technique revealed that D-fructose (50 mmol/l) significantly (P < 0.01) suppressed the acrosome reaction of human spermatozoa, while D-mannose did not show a suppressive effect on the acrosome reaction. These results reinforce our hypothesis proposed previously, that a mandatory step in human fertilization is the binding of a D-mannose-binding constituent of the sperm surface to a D-mannose residue in the sperm receptor site on the zona pellucida. In addition, D-fructose may play an important role as an acrosome stabilizing factor in seminal fluid.