Physiological action of oestradiol on the acrosome reaction in human spermatozoa

Abstract

The acrosome is a secretory vesicle located in the sperm head. The acrosome reaction consists in the fusion of the sperm plasma membrane with the external acrosomal membrane. It has been observed that this reaction does not take place in spermatozoa incubated in cervical mucus, hydrogel that contains high concentrations of oestradiol in the peri-ovulatory period. The objective of the present study was to analyse the influence of oestradiol on the acrosome reaction in human spermatozoa to evaluate the possible inhibitory effect of this hormone. Spermatozoa were incubated in progesterone (10.1 nmol l(-1)); oestradiol plus progesterone (oestradiol at 840 pmol l(-1) and progesterone at 10.1 nmol l(-1)), oestradiol (840 pmol l(-1)) and control (without steroidal hormones) for 30 min, 60 min, 240 min and 24 h. The acrosome reaction was evaluated by stain with Hoechst 33258 and fluorescein isothiocyanate-conjugated Pisum sativum agglutinin lectin. Progesterone-incubated spermatozoa showed the highest percentage of acrosome reaction (P < 0.05). Spermatozoa incubated with oestradiol and oestradiol plus progesterone showed the lowest percentage of acrosome reaction. The present study demonstrates the inhibitory role of oestradiol on the acrosome reaction, stimulated by progesterone in human spermatozoa under physiological conditions.

The slower the better: how sperm capacitation and acrosome reaction is modified in the presence of estrogens

“…All studied estrogens affected the onset of acrosome reaction; however, in this case, estrogens significantly reduced the percentage of sperm that completed the acrosome reaction. These results correlate with recent studies (Baldi et al 2000, Vigil et al 2008, which show a decreased ability of sperm to undergo the acrosome reaction after their capacitation with E 2 . Similarly, our results summarizing the state of the acrosome after CaIinduced acrosome reaction correlate with an elevated amount of sperm head TyrP during sperm capacitation in presence of estrogens.…”

“…Estrogens are low during the preovulatory stage and E 2 is associated with sperm longevity (Mbizvo et al 1990), but the situation changes at the time of ovulation, when the concentration of estrogens released with follicular fluid rises (Shaikh 1971). In correlation to our result, the capacitation and acrosome reaction are modulated by higher concentrations of estrogens and these can serve as a sperm-specific selection barrier where inhibiting effect of estrogens on induced acrosome reaction may have a physiological relevance (Vigil et al 2008). Therefore, estrogens may be seen as one of many preferred cryptic female mechanisms to select the best possible sperm to fulfil the task.…”

Nongenomic activation of spermatozoa by steroid hormones: Facts and fictions

“…Our group (Luconi et al, 1999) has shown that a short time in vitro treatment of human sperm with E induces a small rise of intracellular Ca 2+ which interferes with the subsequent Ca 2+ wave stimulated by P. Ultimately, this effect determines a reduction in P-induced AR, although E themselves do not appear to affect the process. These results have been recently confirmed by another group (Vigil et al, 2008). Similar results were obtained with the ER antagonists tamoxifen and ICI 164384 (Luconi et al, 2001), suggesting that the putative receptor involved in the estrogenic response in spermatozoa shows different characteristics respect to classical ERs (see Section 4).…”

“…However, at the concentrations found in the cumulus mass, P induces AR and a fertilizing sperm needs to pass through the cumulus to fertilize an egg. In this light, the inhibiting effect of E on P-induced AR (Luconi et al, 1999;Vigil et al, 2008) may have a physiological relevance: the interplay between the two steroids during sperm transit in the cumulus mass may be important to ensure a correct timing of the process. In addition, the effects of P present in the cumulus matrix Fig.…”

Modulation of spermatozoon acrosome reaction

“…A variety of ligands have been reported to modulate AR exerting their effects by means of receptors at the level of the spermatozoon plasma membrane (Ohzu and Yanagimachi, 1982;Meizel, 1985;Hoshi et al, 1988;Morales et al, 1992;Llanos et al, 1993;Llanos et al, 1995;DelRío et al, 2007;Vigil et al, 2008). Some of these compounds are distributed in specifi c sectors of the female reproductive tract, probably exerting an in situ AR control (DelRío et al, 2007).…”