Biology of Reproduction, Vol 15, 444-456, Copyright © 1976 by Society for the Study of Reproduction

Changes in Antigenic Site Distribution on Rabbit Spermatozoa after Incubation in "Capacitating" Media

¹ Department of Biological Structure, University of Washington, School of Medicine, Seattle, Washington 98195

Ejaculated and epididymal rabbit spermatozoa have been examined for the surface distribution of antigenic sites before and after treatment with incubation media suggested to induce capacitation. The results indicate that isotonic and hypertonic media are effective in removing certain components from the membrane overlying the acrosomal region yielding "bare" patches in the field of hemocyanin-labeled antibody. Cells treated with hypertonic medium often display completely unlabeled acrosomes whereas the postnuclear sheath retains a heavy complement of labeled sites. Freeze-etching demonstrates an extensive surface coat layer over the sperm head which is much less evident over the sperm tail, and this distribution seems to correlate with that of the antibody label. Some preliminary data on the distribution of sperm antibody sites after in vivo incubation are also presented. The results are discussed with respect to the possible destabilization of head membranes preparatory to the acrosome reaction.

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ACKNOWLEDGMENTS Dr. Richard Blandau kindly made available animal handling facilities and critically read the manuscript. Ms. Doris Ringer provided secretarial services and Ms. Peggy O’Neil helped with some of the technical work. This research was supported by USPHS Grant HD-03752 from the National Institutes of Health and Grant BMS 74-23848 from the National Science Foundation.