Correspondence: Luis Bahamondes, Caixa Postal 6181, 13084-971, Campinas, SP, Brazil. Tel: ฀ 55 19 3289 2856. Fax: ฀ 55 19 3289 2440. E-mail: bahamond@caism.unicamp.br INTRODUCTION Progesterone (P) acts on the hypothalamic-pituitary axis and on different organs of the female reproductive tract such as the uterus, ovaries and mammary glands. Among the actions of P are modulation of Gn-RH pulsatility, differentiation of the endometrium, control of implantation, and maturation of the mammary epi- thelium. After the LH peak, which triggers ovulation, The European Journal of Contraception and Reproductive Health Care, 2012; 17: 428–437 Effect of exposure to ulipristal acetate on sperm function María José Munuce * , Carlos Zumoffen * , Juliana Cicaré * , Adriana Caille * , Sergio Ghersevich * and Luis Bahamondes * Laboratory of Reproductive Studies, Clinical Biochemistry Area, School of Biochemical and Pharmaceutical Sciences, National University of Rosario, Argentina, and Human Reproduction Unit, Department of Obstetrics and Gynaecology, School of Medical Sciences, University of Campinas (UNICAMP) and National Institute of Hormones and Women’s Health, Campinas, SP, Brazil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ABSTRACT Objective A pill containing ulipristal acetate (UPA) is used for emergency contraception (EC). Considering that, following its intake, spermatozoa may be exposed to UPA in the female genital tract we intended to evaluate sperm functions after incubation with this compound. Methods Motile spermatozoa were selected by swim-up and were incubated under capacitating conditions with UPA (at concentrations of 1, 10, 100, 1,000, and 10,000 ng/ml) or control medium. The main outcome measures were sperm vitality, sperm protein tyrosine phosphorylation (TyrP), spontaneous acrosomal reaction (AR), and human follicular fluid (hFF)-induced AR. Results Sperm vitality and TyrP pattern were similar between spermatozoa exposed to UPA or control. In addition, spontaneous AR ranged from 14.0 1.5% to 18.0 1.9% after exposure to UPA or control medium without significant differences, and UPA did not prevent hFF-induced AR. Conclusions Incubation of sperm with UPA at concentrations around the expected plasma levels after ingestion of this EC pill (~฀ 100–200 ng/ml) did not modify the signal transduction of TyrP involved in sperm capacitation. Moreover, UPA showed no agonist effect on progesterone receptors because it did not induce AR. Considering that progester- one in hFF is essential for AR induction, and UPA did not prevent the hFF-induced AR, an antagonist action of UPA on the AR is unlikely. KEYWORDS Spermatozoa; Ulipristal acetate; Acrosomal reaction; Sperm function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . © 2012 The European Society of Contraception and Reproductive Health DOI: 10.3109/13625187.2012.725877