Distribution pattern(s) of sperm protein at 22 kDa (SP22) on fresh, cooled and frozen/thawed equine spermatozoa and expression of SP22 in tissues from the testes and epididymides of normal stallions.

Contents The objectives of this study were to (i) verify localization of SP22 on fresh, cooled, and frozen/thawed equine spermatozoa and to (ii) determine SP22 mRNA and protein expression in equine testicular and epididymal tissues. Immunocytochemistry and Western blots were performed on the spermatozoa samples. Northern blots and Western blots were performed on the tissue samples. The immunocytochemistry revealed the presence of SP22 in all samples tested. The fresh spermatozoa stained predominantly over the equatorial segment as did the samples cooled for 1 and 2days. The samples cooled for 3days, and the frozen/thawed samples had an increased proportion of no staining. The Western blots revealed SP22 was present on all semen samples tested. The Northern blot of the tissues revealed a 1.0kb mRNA transcript present in each of the tissues, and the Western blot revealed the presence of SP22 in each of the tissues. As expected, SP22 was found to be altered on cooled and frozen/thawed spermatozoa. Our results suggest that the equatorial pattern is the normal pattern in spermatozoa, while a complete loss of SP22 from the surface of spermatozoa seems to be the staining pattern indicating the most extreme abnormality with scattered staining of the head indicating intermediate damage.