Calcium ionophore-induced acrosome reaction correlates with fertilization rates in vitro in patients with teratozoospermic semen

The aim of this study was to determine the relationship between calciumionophore A23187-induced acrosome reaction (AR) and sperm fertilizingability. Semen samples remaining after preparation for standard IVF werestudied in 109 patients who had sperm concentrations > or =20 x10(6)/ml. Ionophore-induced AR was performed on motile spermatozoa selectedby centrifugation on a Percoll gradient. Semen analysis was performed usingstandard methods. Patients with higher (>50%, n = 76) fertilizationrates had significantly higher ionophore-induced AR than patients withlower (<50%, n = 33) fertilization rates (49 +/- 14 versus 38 +/- 21%, P< 0.05). When the data from all patients were analysed by logisticregression, only the percentage sperm motility in insemination medium andionophore-induced AR were significantly related to fertilization rates.Similar results were also obtained when the data from a subgroup ofpatients with poor (<15% normal) sperm morphology were analysed.However, when patients with normal sperm morphology > or =15% wereanalysed separately, only sperm count and the percentage of spermatozoawith progressive motility in semen were significantly related tofertilization rates. In conclusion, ionophore- induced AR was significantlyrelated to fertilization rates in vitro mainly in patients withteratozoospermic semen. Tests for ionophore- induced AR may provideadditional information about sperm fertilizing ability but may not indicatespecific defects of the physiological AR.