Optimal dose and duration of exposure to artificial stimulants in cryopreserved human spermatozoa

Poor sperm motility after cryopreservation is associated with infertility. For any pharmacological stimulation to be of clinical value, its effect in enhancing motility and other motion characteristics should be maintained for at least 1 hour.

Three motility stimulants (pentoxifylline, caffeine and 2-deoxyadenosine) were incubated with post-thaw semen samples from 11 healthy donors for 0, 30, 60, 120 and 180 minutes. The final concentrations used were 2.5 mM., 5 mM. and 10 mM. for pentoxifylline; 1 mM., 2 mM. and 5 mM. for caffeine, and 0.5 mM., 1 mM. and 2.5 mM. for 2-deoxyadenosine. Percent motility and changes in motion characteristics were measured on a computer assisted semen analyzer.

Compared to controls (0 minutes, no stimulant), an immediate increase in motility and other motion parameters was noted with all 3 stimulants. All stimulants caused a significant increase in percentage motility at all periods studied (p < 0.01). Similarly, pentoxifylline increased other motion parameters at the 2.5 mM. concentration (p < 0.01), caffeine was effective in increasing curvilinear velocity, average path velocity and amplitude of lateral head displacement (p < 0.01) at 5 mM., and 1 and 2.5 mM. of 2-deoxyadenosine increased the curvilinear velocity, straight line velocity, average path velocity and amplitude of lateral head displacement (p < 0.01). Among all stimulants only 2-deoxyadenosine increased linearity only at the 1 mM. concentration.

Our study suggests that these stimulants, when used at optimum concentrations, can maintain the improved sperm quality for durations longer than the minimum needed for fertilization. This finding may be significant in improving the poor semen quality observed after cryopreservation in oligospermic samples and in semen specimens from cancer patients.