Similarly, several components of the UPP showed a statistically significant expression change on Day 18 in expression analysis. On the basis of our studies of sperm ubiquitin in infertile men, we could expect an overall reduction in the percentage of presumably normal spermatozoa with background levels of surface ubiquitin (see Fig. 3, A and B) and predict an overall increase of the sperm ubiquitin levels in THP- and DNB-exposed rats. While we indeed observed a significant reduction in the normal sperm percentage after THP exposure, the overall sperm ubiquitin values were actually lower in the exposed animals than in the control animals on Days 30 and 42.
Sperm fragmentation and widespread tubular disease with THP exposure could explain this seeming paradox. Although the detached heads and tail fragments did show intense ubiquitin immunostaining in epifluorescence microscopy, their small size reduced the individual cell reading in the flow cytometer to a level that was only a small fragment of the reading obtained for intact, whole spermatozoa, regardless of their ubiquitin expression.