The rapid induction of the acrosome reaction of human spermatozoa by electropermeabilization

Human spermatozoa are usually prepared for in vitro fertilization (IVF) by centrifugal washing and incubation in albumin based media. This is an inefficient technique contributing to poor IVF prospects, false-negative scores in the sperm penetration assay (SPA), and inadequate quantification in the sperm chromosome assay (SCA). High yields of fusiogenically functional sperm were rapidly and efficiently prepared by exposing sperm suspensions to an electrical pulse of 750 to 1500 V cm^-1 for 2.5 msec. This process was calcium-dependent, and sperm incorporation into zona-free hamster eggs exhibited a linear relationship with Ca²⁺. At voltages >1500 V cm^-1, penetration declined. Sperm from subfertile men demonstrated significantly increased penetration after electropermeabilization. Sperm development was not hindered and in the SCA, yields of sperm metaphases approaching 100% were achievable.