CHANGES IN PROTAMINE-1 DISTRIBUTION IN HUMAN SPERM NUCLEUS DURING IN-VITRO SPERM-OOCYTE INTERACTION - AN IMMUNOELECTRON MICROSCOPIC STUDY

Objective: To determine whether the process of sperm nuclear destabili zation would begin before sperm-oocyte fusion in humans. Design: Chang es in the distribution of human protamine 1 were investigated in human spermatozoa from the ejaculate, in spermatozoa selected by swim-up or Percoll techniques, and in spermatozoa bound to zona pellucida (ZP) f rom oocytes that failed to fertilize in an IVF program. Setting: Cente r for Infertility and Assisted Reproductive Technology, and university departments, Patient(s): Fifteen couples undergoing an IVF program. I ntervention(s): Women underwent a similar superovulation induction pro tocol that consisted of GnRH agonist associated with hMG. Main Outcome Measure(s): Comparative immunoelectron microscopic study of sperm nuc leus labeling with an anti-human protamine 1 specific protamine monocl onal antibody. Result(s): After selection by swim-up or by Percoll, sp ermatozoa show a significantly lower nuclear labeling than in the ejac ulate, After binding to the ZP, labeling increases, more in spermatozo a selected by swim-up than by Percoll, but, after Percoll selection, l abeling in zona-bound spermatozoa is lower than in the ejaculate. Conc lusion(s): In humans, sperm binding to the ZP induces differences in t he accessibility of the anti-human protamine 1 antibody, which are con sistent with structural rearrangements of the DNA-nucleoproteins compl ex. These modifications must be a prelude to sperm decondensation, pro tamines replacement by histones, and subsequent reactivation of the sp erm genome in the oocyte.