SPERM MOTION PREDICTS FERTILITY IN MALE HAMSTERS TREATED WITH ALPHA-CHLOROHYDRIN

An understanding of the relationship between altered sperm motion and sperm function (fertility) is important when interpreting the biologic al significance of toxicant-induced changes in sperm velocity in roden t test species, Previous studies showed that a brief (4-day) exposure of male hamsters to the model chemical alpha-chlorohydrin (ACH) result s in significant deficits in epididymal and uterine sperm velocity, wh ich are associated with both a delay and a failure of fertilization in vivo. To characterize this effect in terms of fertility, similarly tr eated male hamsters were bred to untreated females and pups were count ed the day before parturition. ACH treatment resulted in a dose-depend ent decline in the percentage of sperm-positive females that were preg nant at the end of gestation (100, 78, 67, 22, and 0 where males were treated with 0, 33, 49, 66, and 83 mg ACH/kg/day, respectively), Cauda epididymal sperm from the same males were assayed for motion characte ristics using computer-assisted sperm analysis (CASA), and for fertili zing ability in vitro. While the percentage of motile sperm was unaffe cted by ACH treatment, sperm velocity declined in a dose-dependent man ner at all ACH treatment levels, Futhermore, the velocity of sperm fro m infertile males was shifted downward consistently across the entire velocity distribution. Since treated males tended to either be inferti le (no pups) or have near normal litter size, the correlation between sperm velocity and litter size was nonlinear. Therefore, logistic regr ession models using velocity cut-off values were the most useful model s for predicting fertility. These results support the contention that fertility relies on there being a sufficient number of sperm that exce ed a velocity threshold. Sperm from treated males were also less likel y to support in vitro fertilization (IVF), providing further evidence of impaired sperm function associated with acute exposure to ACH.