Function of human epididymal spermatozoa

Human epididymal spermatozoa taken from caput, corpus, and cauda were investigated to determine their fertilizing capacity (22 epididymides from 11 patients who had undergone orchidectomy because of prostatic cancer). The following functions, which have been reported to correlate positively with the fertilization rate, were determined: motility and progressive motility, chromatin condensation (assessed by aniline blue staining), acrosin activity, and induction of acrosome reaction by low temperature. In addition, stimulation of motility by pentoxifylline and phosphatidylcholine was examined. The results showed that motility, progressive motility, normal chromatin condensation, and inducible acrosome reaction increased from the caput to the cauda epididymidis, whereas acrosin activity was normal in all sections. Stimulation of progressive motility, especially that of caput spermatozoa, could be achieved by both pentoxifylline and phosphatidylcholine, the latter being definitely superior. In conclusion, our study confirmed that human spermatozoa in physiological status undergo several steps of maturation during the epididymal transit. Stimulation of sperm motility by phosphatidylcholine may be helpful for patients in whom epididymal spermatozoa are used for assisted reproduction.