Premature acrosome reaction in spermatozoa from lead-exposed mice

Lead-exposed mice were found to show a significantly increased frequency of acrosome-reacted spermatozoa. The number of spermatozoa bound to the zona pellucida of denuded mouse eggs was also significant increased, probably as a result of an acceleration of the processes involved in the capacitation of the spermatozoa and thereby of the acrosome reaction. However, the ability of spermatozoa from the lead-exposed mice to penetrate the investments surrounding the oocyte, e.g. the zona pellucida and the plasma membrane, was significantly reduced. No significant differences were detected in the frequency of motile spermatozoa or in the swimming speed between spermatozoa from the lead-exposed and the control group of mice. These results indicate that the previously observed reduction in fertility after exposure to lead, may be due to a disturbed interaction of the spermatozoa with the oocyte.