Recombinant human zona pellucida glycoprotein 3 induces calcium influx and acrosome reaction in human spermatozoa

Recombinant human ZP3 (rhuZP3) generated by Chinese hamsterovary cells transfected with a plasmid containing human ZP3cDNA was used to study the acrosome reaction (AR) and intracellularcalcium fluxes in capacitated human spermatozoa. Conditionedmedium containing rhuZP3 significantly induced the AR (P <0.005)in 59.4 ± 4.7% of spermatozoa (control = 8.5 ±3.1%) and caused complete acrosomal loss in a further 17.2 ±3.8% of cells (control = 3.7 ± 0.7%; mean ± SEM,n = 5). Sperm motility was not affected and acrosomal exocytosisin response to rhuZP3 was also shown to be time-dependent. Basalconcentrations of sperm intracellular calcium were measured(82 ± 7 nM; mean ± SEM, n = 9). A transient increasein intracellular calcium (typically up to 400–450 nM)occurred within 1 min of rhuZP3 addition and was followed bysustained lower values of calcium (200–400 nM). Theseresponses were dependent on the amount of rhuZP3. This is thefirst report of zona protein-induced changes in intracellularcalcium levels in human spermatozoa. The results support thepremise that ZP3 is an aganist of the human sperm AR and thatrhuZP3 generated in a eukaryotic cell is effective in this respect. acrosome reaction/calcium/human/spermatozoa/ZP3