Objective: To determine if the motility stimulants, caffeine (7 mM), pentoxifylline (3 mM), 2-deoxyadenosine (3 mM), and a combination of the three would induce hyperactivated (HA) motility.
Design: Controlled laboratory study of stimulants using cryopreserved semen from 10 donors at three time points.
Setting: The study was performed in the Andrology Laboratory at Prince Henry's Institute of Medical Research Clayton, Victoria, Australia.
Interventions: Stimulants in doses maximally effective for stimulation of motility were incubated with suspensions of previously cryopreserved sperm.
Main outcome measures: Motility characteristics (curvilinear velocity [VCL], linearity [LIN], and maximum amplitude of lateral head displacement [ALHmax]) were derived using the single cell track facility of the CellSoft computer-automated semen analyzer (Cryo Resources Ltd., Montgomery, NY). Videotapes were visually inspected, and 125 sperm cell trajectories exhibiting characteristic HA behavior were identified. The HA motility thresholds (5th or 95th centiles) were as follows: VCL > 74 microns/s, LIN < 74%, and ALHmax > 4.7 microns. Cells with motility characteristics outside these limits were regarded as HA. The significance of the effect of the stimulants on the proportion of sperm exhibiting HA was examined by Poisson regression analysis.
Results: Sperm washing (removal of the cells from the cryoprotectant) and swim-up caused significant changes in the VCL and straight line velocity and a twofold (5.6% to 11.9%) increase in the proportion of HA cells. In the presence of motility stimulants, the proportion of HA cells was significantly increased threefold (11.9% to 32.5%) above that seen in the control washed sperm. Hyperactivated motility declined after 1 to 2 hours, but 2-deoxyadenosine demonstrated a prolonged effect.
Conclusion: These motility stimulants that affect adenosine 3':5' monophosphate in human sperm stimulate cyclic hyperactivation.