Effects of phosphodiesterase inhibitors caffeine and pentoxifylline on spontaneous and stimulus-induced acrosome reactions in human sperm.

OBJECTIVE

To determine whether the phosphodiesterase inhibitors caffeine and pentoxifylline influence the acrosome reaction in the conditions in which they are currently used as sperm movement enhancers.

DESIGN

The frequency of acrosome reaction occurring spontaneously in capacitating media or induced by physiological (follicular fluid [FF]) and artificial (ionophore A23187) stimuli was compared in the presence and absence of the phosphodiesterase inhibitors.

SETTING

Private hospital and research laboratory.

PATIENTS, PARTICIPANTS: Patients undergoing routine semen examination before in vitro fertilization (no pathology detected) and healthy sperm donors.

INTERVENTIONS

None.

MAIN OUTCOME MEASURE

Percentage of acrosome-reacted sperm determined with the use of fluorescein-labeled Pisum sativum agglutinin as acrosomal stain.

RESULTS

Caffeine alone augmented the frequency of acrosome reaction, but this effect was not observed with pentoxifylline alone. However, pentoxifylline increased sperm responsiveness to the acrosome reaction-inducing stimuli, FF and ionophore A23187.

CONCLUSIONS

The promotion of spontaneous acrosome reaction may counteract the benefits from application of caffeine as motility stimulant. On the other hand, the sensitization to physiological acrosome reaction stimuli is expected to contribute to the improvement of sperm fertilizing ability by pentoxifylline and make this drug a potential candidate for the treatment of acrosome reaction anomalies.