Equivalence of 'non-IgG binding' and 'acrosomeless' sperm populations from the female genital tract of the rabbit

Spermatozoa were recovered from the ejaculate, vagina, uteri and oviducts of mated does between 2.5 and 14 h p.c. For each sample, the proportion of spermatozoa exhibiting no binding of IgG from normal serum, after air drying and acetone fixation, was compared with the proportion of acrosomeless spermatozoa as assessed by staining with eosin and fast green. The correlation was excellent (r = 0.97; P less than 0.001) suggesting that failure of acetone-fixed spermatozoa to bind IgG from normal serum may reflect acrosome absence rather than 'acrosomal uncoatibility'. Usually the proportion of immunofluorescence negative or acrosomeless spermatozoa was about 10% in the ejaculate; 15% in the vagina; 25% in the uterus and 70-100% in the oviducts. This phenomenon is not an air-drying artefact, and seems to be independent of flushing medium.