Acrosome reactivity in spermatozoa of different morphology in response to stimulation with follicular fluid

The ability of the morphologically abnormal spermatozoon to undergo the processes necessary for fertilization is unknown; one of the essential processes is the acrosome reaction. In order to assess this, spermatozoa from 10 known fertile donors were incubated with either follicular fluid or Earle's medium containing 3 mg/ml bovine serum albumin at 37 degrees C for 6 h. The spermatozoa were then stained with 2% Trypan Blue prior to being fixed in glutaraldehyde and stained for the presence of the acrosomal cap using the triple stain. Fifty live spermatozoa in each of four morphological categories (normal head, large head, small head, abnormal neck or tail) were examined and the number of acrosome-reacted spermatozoa determined. There was a significant difference between the morphological groups in the baseline number of acrosome-reacted spermatozoa, determined by examining sperm samples incubated in Earle's medium; however, the number of spermatozoa undergoing the acrosome reaction in response to stimulation with follicular fluid (i.e. the number of spermatozoa acrosome-reacted in follicular fluid minus the number acrosome-reacted in Earle's medium) was similar for all morphological groups. This suggests that abnormal sperm morphology did not affect the response of spermatozoa to activation of the acrosome reaction by exogenous stimuli.