Use of the SPA in assessing toxic effects on male fertilizing potential

The sperm penetration assay (SPA), which involves the use of zona-free hamster eggs to assess fertilizing potential of human spermatozoa, has the capability of evaluating the functional capacity of sperm. If men are exposed to a toxic insult that could result in impaired fertility, this has been monitored historically by determining the routine semen parameters of concentration, motility, and morphology. The lack of availability of the SPA for evaluating toxic exposure in field studies has hampered its utilization. The purpose of this article is to illustrate the use of the SPA in a specific field study and to describe two recent innovations in the SPA that make its use more accessible for field studies. These two innovations are shipping semen samples in TEST-yolk buffer by overnight express to a central laboratory for testing and using frozen hamster eggs in the test. The report is divided into the following three major sections: I. Kunia study; II. TEST-yolk buffer modifications of SPA; and III. Use of frozen eggs in SPA.