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 s permatozoa from a group of unselected male partners of couples undergo ing in-vitro fertilization (IVF). We evaluated progesterone-stimulated intracellular Ca2+ ([Ca2+](i)) and percentage increase in acrosome re action in the same sperm sample used for oocyte inseminations, [Ca2+]( i) was measured with a fluorimetric method, while the acrosome reactio n was assessed using a fluorescent probe (fluorescein isothiocyanate-l abelled peanut lectin), The average percentage [Ca2+](i) as well as th e rate of increase in the frequency of acrosome reaction following pro gesterone 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-stimu lated [Ca2+](i) and acrosome reaction increases (r = 0.78 and r 0.79 r espectively) were observed, Furthermore, in cases of fertilization fai lure, no increase of [Ca2+](i) or acrosome reaction was observed in re sponse to progesterone with the exception of one case, Our results ind icate that [Ca2+](i) and acrosome reaction increases in response to pr ogesterone can be of value in the prediction of sperm fertilizing abil ity, As the two parameters were significantly correlated to each other (r = 0.86), the two assays have similar IVF predictive value and migh t be used interchangeably as a diagnostic tool in the assignment of ma le patients to the different kinds of assisted fertilization technique s.