Dithiothreitol effects on the viscosity and quality of human semen.

Objective: To determine the effects of treatment with dithiothreitol (DTT) on seminal viscosity, consistency, and sperm motility, motion characteristics, and morphology.

Design: Prospective, in vitro study.

Setting: University teaching hospital.

Patients: Semen donors and patients of the infertility program. Experiment 1, n = 34; experiment 2, n = 82. Sufficient seminal volume for use was the only selection criterion.

Interventions: Experiment 1: semen was combined with 5.9 mM DTT solution 1:1 (vol/vol), combined with distilled water 1:1 (vol/vol), or untreated. Experiment 2: semen was combined with 5.9 mM DTT solution 1:1 (vol/vol) or untreated.

Main Outcome Measures: Seminal consistency and viscosity, percentage of motile sperm, sperm motion characteristics (straight line velocity, curvilinear velocity, mean linearity, and angle of lateral head displacement), sperm concentration, and sperm morphology.

Results: Treatment of semen with DTT reduced seminal consistency and viscosity. Treatment with DTT had no effect on sperm concentration or percentage motile sperm. Sperm velocity was reduced by DTT treatment, particularly in semen that had normal initial consistency. Morphology of sperm in semen exhibiting abnormal initial consistency was unaffected by DTT.

Conclusion: Dithiothreitol effectively induced liquefaction of nonliquefied semen in vitro and had minimal effects on the sperm motility, motion characteristics, and morphology. Evaluation of DTT effects on the chromatin and on other functional traits of human sperm must be conducted before its use can be advocated.