Effects of pentoxifylline and progesterone on human sperm capacitation and acrosome reaction

This study was designed to test the effects of pentoxifylline and progesterone upon capacitation of fresh human spermatozoa. Capacitation and acrosomal integrity were assessed using the fluorescent probe chlortetracycline on spermatozoa co-stained with a supravital fluorescent dye, Hoechst 33258. Hyperactivated motility was measured using computer-assisted movement analysis. After exposure to pentoxifylline (1 mg/ml; 30 min), the fluorescent 'B' pattern, characteristic of capacitated, acrosome-intact cells, increased significantly (P < 0.01), though no increase in 'AR' pattern, characteristic of acrosome-reacted cells, was detected. There was a significant increase in hyperactive motility (P < 0.001). Exposure to progesterone (1 microgram/ml; 60 min) resulted in a significant increase in 'B' pattern (P < 0.05) and 'AR' pattern (P < 0.005), though no effect on the expression of hyperactivation was detected. No effect upon hyperactivation was detected on exposure of fresh or cryopreserved spermatozoa to a physiological range of progesterone concentrations (0.1-1000 ng/ml). Sequential exposure to pentoxifylline then progesterone resulted in a significant increase in 'B' pattern, acrosome loss and hyperactivation. Sperm viability was not affected in any treatment group. These observations suggest that pentoxifylline and progesterone affect capacitation through independent mechanisms. Stimulation of both capacitation and acrosome reaction resulted from sequential exposure to pentoxifylline and progesterone. This may have implications for sperm handling for assisted reproductive techniques.