Changes in movement characteristics of human spermatozoa along the length of the epididymis.

It has been established in laboratory mammals that sperm motility and fertilizing capacity develop during epididymal transit, but sperm maturation along the human epididymis is less well characterized. Spermatozoa were prepared from 5 regions of 8 epididymides from 8 prostatic carcinoma patients undergoing castration and from 8 epididymal spermatocoeles located adjacent to the head of the epididymides and the testes of 5 patients. Sperm movement was characterized by computer-aided sperm analysis (CASA), and percentage motility was estimated by conventional methods. The efferent ducts and spermatocoeles contained the same percentage of motile spermatozoa with similar kinematics. Percentage motility increased from 22.9 +/- 4.8 (mean +/- SEM) in the efferent ducts to a maximum of 68.3 +/- 7.9 in either the mid- or distal corpus epididymidis and declined in the cauda region. Straight line velocity increased from 20.3 +/- 3.7 microns/sec to reach a plateau value of 44.0 +/- 5.3 microns/sec in the mid-corpus epididymidis; this was more marked than the increase in curvilinear velocity, although the trend was the same. Similar trends in linearity and straightness of the swim paths were not accompanied by any significant changes in the amplitude of lateral head displacement. This objective quantification of sperm movement documents the maturation of sperm motility in the human epididymis, confirming that this maturation pattern is similar to that in other mammals.