Innocuity of tetradecyl-dimethyl-benzyl ammonium fluoride on the DNA of human spermatozoa

Abstract

Tetradecyl-dimethyl-benzyl-ammonium fluoride (TDBAF) is a powerful new spermicide. In cases of failure of local contraception, there is a theoretical risk that a spermatozoon exposed to a sublethal concentration of spermicide might suffer DNA strand breaks, with transmission of damaged DNA to the oocyte. The present study aims to ascertain the innocuity of TDBAF in this regard. Spermatozoa from 32 fertile men were exposed to a sublethal concentration of TDBAF. The degree of DNA fragmentation was measured by modified terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin end labeling (TUNEL) assay, pulsed field gel electrophoresis of purified sperm DNA and radioenzymatic labeling. With the TUNEL assay, a statistically significant increase in sperm labeling was observed after TDBAF treatment compared to the controls. However, pulsed field gel electrophoresis and enzymatic labeling of purified DNA showed no evidence of augmented DNA fragmentation in TDBAF-treated sperm. Under electron microscopy, TDBAF caused sperm chromatin decondensation. In the TUNEL assay, this phenomenon would allow easier access of terminal transferase to its DNA substrate, explaining the apparent increase in DNA fragmentation in the presence of TDBAF. In conclusion, the use of TDBAF as a spermicide does not place progeny at heightened risk of abnormalities should pregnancy occur. In regard to the TUNEL assay, we suggest that pretreatment of spermatozoa with TDBAF promotes a more accurate measurement of sperm DNA fragmentation.