INDUCTION OF ACROSOME REACTION IN HUMAN SPERMATOZOA ACCELERATES THE TIME OF PRONUCLEUS FORMATION OF HAMSTER OOCYTES AFTER INTRACYTOPLASMIC SPERM INJECTION

Objective: To assess the relationship between the incidence of acrosom e reaction (AR) and the timing of pronucleus (PN) formation after intr acytoplasmic sperm injection (ICSI). Design: Prospective study. Settin g: Infertility Research Center, Jell Women's Hospital. Main Outcome Me asure(s): Human semen obtained from fertile donors was prepared by one of the following methods: washing only (washed control); Percoll grad ient; pentoxifylline; human follicular fluid (FF); pentoxifylline + FF ; or platelet-activating factor (PAF) treatment. The AR of each group was assessed by fluorescein isothiocyanate-conjugated Pisum sativum ag glutinin or Arachis hypogea agglutinin. Spermatozoa of washed control, pentoxifylline + FF, and PAF treated groups, with significantly highe r AR rate than others, were injected into mature hamster oocytes. Sper matozoon-injected oocytes were cultured for 6, 9, 12, or 15 hours. The n they were stained with Toluidine blue for PN formation examination u nder a light microscope. Result(s): Acrosome reaction rates of washed control, Percoll gradient, pentoxifylline, FF, pentoxifylline + FF, an d PAF treated groups were 10.5% +/- 2.6%, 10.3% +/- 1.7%, 16.4% +/- 1. 8%, 24.8% +/- 5.6%, 28.4% +/- 3.8%, and 33.3% +/- 5.2%, respectively. Pronuclear formation rate in washed control, pentoxifylline + FF, and PAF treated groups were 5.6%(3/54), 19.0% (11/58), and 18.9% (10/53) a t 6 hours; 32.7% (18/55), 51.8% (29/56), and 57.4% (31/54) at 9 hours; 36.1% (22/61), 53.6% (30/56), and 50.0% (27/54) at 12 hours; and 47.2 % (25/53), 64.8% (35/54), 53.6% (30/56) at 15 hours after ICSI. Pronuc lear formation rate was significantly higher in pentoxifylline + FF, a nd PAF treated groups than that in the washed control group at 6 and 9 hours after ICSI. Conclusion(s): Pronuclear formation of oocytes take s place faster on those that were injected with acrosome-reacted sperm atozoon than those injected with acrosome-intact spermatozoon. It coul d be concluded that induction of the AR of spermatozoa accelerates the time of PN formation and early development of the embryo in ICSI.