Morphological and Numerical Changes of Round Cells Derived from Seminiferous Epithelium in Equine Epididymides

Morphological and quantitative changes in round cells in different areas of the equine epididymis were examined. Their correlation with the number of round cells ejaculated into semen was also analyzed. In the present study, 23 semen samples collected from 21 horses (5-28 years old) and epididymal perfusate collected from various sections of the epididymis of four other horses (3-17 years old) were analyzed. For each sample, round cells were classified into less than 7.0um in diameter (SC), between 7.0 and 12.5um (MC) or greater than 12.5um (LC), and the number and their morphology were examined. The average number of round cells per 1, 000 sperms decreased from the head to the tail of the epididymis: 45.01 in the epididymal head; 2.07-4.87 in the epididymal body; and 8.19 in the epididymal tail. In addition, 69.2% of the round cells in the epididymal tail were alive. MC was most prevalent in the efferent duct and the epididymal duct, accounting for 54.9 - 71.4%. On the other hand, the ratio of SC increased from 14.7% in the efferent duct to 26.2 - 42.2% in the epididymal duct. The rate of LC was 16.8% in the efferent duct and decreased to 2.2 - 4.7% toward the epididymal duct. The average number of round cells in ejaculated semen was low (0.20), and their sizes had the following distribution: SC 4.8%; MC 90.1% and LC 5.1%, showing remarkably higher percentage of MC compared to the epididymal duct. The above findings showed that a majority of round cells disappear while passing through the epididymis. It also indicated that the round cells ejaculated into semen are less than 1% of those seen in the head of the epididymis.