Human sperm immobilizing activity of aminophenyl arsenic acid and its N-substituted quinazoline, pyrimidine, and purine derivatives: protective effect of glutathione.

We examined the potential toxicity of pentavalent organic arsenicals for human sperm. We used computer-assisted sperm analysis to examine the effects of three aminophenyl arsenicals and their nine N-substituted quinazoline, pyrimidine, and purine derivatives on human sperm motility and kinematics in human semen and medium. Among the arsenicals examined, (aminophenylazo)-phenyl arsonic acid and its N-substituted pyrimidine derivative PHI-370 (2-methylthio-4-[(4'-aminophenylazo)-phenylarsonic acid] pyrimidine) exhibited rapid sperm immobilizing activity in medium with EC(50) values of 77 and 82 microM, respectively, and t(1/2) of < 3 min. Molecular modeling analysis indicated that sperm-immobilizing organic arsenicals exhibit high dipole moments (>7 Debyes). Sperm immobilizing activity of these arsenicals was completely abrogated in the presence of seminal plasma. Furthermore, coincubation of motile sperm with PHI-370 in the presence of reduced glutathione (GSH) resulted in dose-dependent protection of sperm motility and sperm motion parameters. Coincubation of the arsenical with GSH at a molar ratio of 1:20 resulted in 95% retention of sperm progressive motility. The mean values of the other sperm movement characteristics also showed > 90% protection. These observations suggest that the rapid sperm immobilizing activity of these pentavalent arsenicals may be as a result of direct binding of the arsenical with the sperm thiol components essential for sperm motility as well as induction of oxidative damage by disruption of sperm cell's antioxidant system. Sodium arsanilate and its N-substituted pyrimidine derivative, PHI-370, are useful probes to further evaluate the mechanism of pentavalent arsanilate-induced human sperm dysfunction.