CONICET | Buscador de Institutos y Recursos Humanos

Objective: Ulispristal acetate (UPA) is a selectiveprogesterone receptor modulator widely used for emergency contraception (EC). Thedescribed main mechanism of action is by inhibiting or delaying ovulation; however,the postovulatory effects of the drug are still on debate. Therefore, the aim of this studywas to determine whether UPA could interfere with human spermfertilizing ability. Study design: Human motile spermatozoa wereincubated under capacitating conditions with or without UPA, and then used to inseminate human tubal explants, mouse cumulus-oocytecomplexes and zona-free hamster eggs. The ability of UPA to interact with humansperm progesterone (P)-binding sites was investigated by incubating the cellswith fluorescent-labeled P andanalyzing them by fluorescence microscopy. Results: UPAdid not affect the ability of human sperm to bind to human tubal tissueexplants surface, or to penetrate the mouse cumulus mass and the zona-freehamster eggs. In addition, concentrations of UPA much higher than those presentin the plasma of EC pill users were required to bind to human sperm P-bindingsites. Conclusions: Our study supports a lackof an agonist or antagonist action of UPA on different functional parametersassociated with the fertilizing ability of human sperm. Implications: This study provides new functional evidencesupporting that the contraceptive action of UPA is not related to effects on humansperm cells, contributing to a better understanding of the mechanism of actionof UPA as EC.