Regulation of hyperactivation of hamster spermatozoa by progesterone

Aim: Although it is accepted that progesterone (P) induces acrosome reaction through non‐genomic regulation, it is not well known if P also affects hyperactivation of sperm. Methods: Hamster spermatozoa were hyperactivated by incubation for 4 h on modified Tyrode's albumin lactate pyruvate medium and recorded on a DVD via a charge‐coupled device camera attached to a microscope with phase‐contrast illumination and a small CO2 incubator. Phosphorylation of proteins was detected by western blotting using antiphosphotyrosine antibodies. Results: Sperm hyperactivation was significantly increased and accelerated by a non‐genomic signal of P. Although acceleration of motility of hyperactivated sperm occurred with 10, 20 and 40 ng/mL P, the most effective concentration was 20 ng/mL. Progesterone also significantly increased 80‐kDa tyrosine phosphorylation of sperm proteins. Both extracellular Ca2+ and albumin were essential for sperm hyperactivation, and the former was also essential for maintaining sperm flagellar movement. Moreover, phospholipase C (PLC) was associated with the regulation of hyperactivation by P. Conclusion: It is likely that P regulates sperm hyperactivation by a non‐genomic signal in relation to tyrosine phosphorylation and PLC. (Reprod Med Biol 2008; 7: 63–74)