INTRACELLULAR CALCIUM INCREASE AND ACROSOME REACTION IN RESPONSE TO PROGESTERONE IN HUMAN SPERMATOZOA ARE CORRELATED WITH IN-VITRO FERTILIZATION

In this study we have investigated responsiveness to progesterone in spermatozoa from a group of unselected male partners of couples undergoing in-vitro fertilization (IVF). We evaluated progesterone-stimulated intracellular Ca2+ ([Ca2+](i)) and percentage increase in acrosome reaction in the same sperm sample used for oocyte inseminations, [Ca2+](i) was measured with a fluorimetric method, while the acrosome reaction was assessed using a fluorescent probe (fluorescein isothiocyanate-labelled peanut lectin), The average percentage [Ca2+](i) as well as the rate of increase in the frequency of acrosome reaction following progesterone challenge were significantly lower (P < 0.005) in the group of patients with a fertilization rate < 50%, In addition, significant correlations between the fertilization rate and the progesterone-stimulated [Ca2+](i) and acrosome reaction increases (r = 0.78 and r 0.79 respectively) were observed, Furthermore, in cases of fertilization failure, no increase of [Ca2+](i) or acrosome reaction was observed in response to progesterone with the exception of one case, Our results indicate that [Ca2+](i) and acrosome reaction increases in response to progesterone can be of value in the prediction of sperm fertilizing ability, As the two parameters were significantly correlated to each other (r = 0.86), the two assays have similar IVF predictive value and might be used interchangeably as a diagnostic tool in the assignment of male patients to the different kinds of assisted fertilization techniques.