Effects of in vivo and in vitro incubation on capacitation of equine spermatozoa

Abstract

Equine spermatozoa were subjected to both in vivo and in vitro treatment and subsequently evaluated for evidence of capacitation. In vivo treatments consisted of incubating freshly ejaculated spermatozoa for intervals of 2, 4, 6, and 8 hrs in utero while in vitro treatments included incubation of spermatozoa for either 5 or 15 min in media with osmolalities of either 258, 302, 372, or 418 m0s/kg. Following either in vivo or in vitro treatments, spermatozoa were evaluated for (1) loss or retainment of fluorescent label, (2) changes in oxygen consumption, and (3) an ability to penetrate the zona pellucida of equine ova. No motile spermatozoa were observed to fluoresce during any portion of the study. However, non-motile spermatozoa readily fluoresced under UV light. There was a trend of a lower percentage of non-motile spermatozoa to fluoresce following incubation of either 4, 6, or 8 hrs in utero compared to the 2-hr incubation or the in-vitro controls. Incubation of spermatozoa in media of various osmolalities appeared to have no effect on loss or retainment of the label regardless of medium tonicity or incubation interval.