Extra-epididymal spermatosoa express nuclear abnormalities

Extra-epididymal spermatozoa account for approximately a third of all sperm atozoa found in the normal human ejaculate. Whilst remaining outside of the testes at core body temperature, the functional competence of spermatozoa, including cell motility and fertilizing capacity, diminishes. By examining spermatozoa found in the seminal fluid of recently vasectomized men, this study has investigated the nuclear changes that occur in spermatozoa whilst persisting in sites distal to the epididymis. Spectral recordings of sperm atozoa stained with the nucleic acid dye, toluidine blue and the sperm chro matin structure assay (SCSA) were performed. Toluidine blue staining of hum an sperm DNA is an effective predictor of abnormal protamine disulphide cro sslinking and chromatin condensation. Using flow cytometry, the SCSA determ ines the sensitivity of sperm DNA to acid-induced denaturation, providing a measure of chromatin and DNA damage. Abnormal protamine disulphide crossli nking and chromatin condensation was significantly higher in spermatozoa fr om patients after vasectomy when compared to normozoospermic controls (p < 0.01). Additionally, spermatozoa from vasectomized donors were significantl y more sensitive to acid-induced denaturation than were normozoospermic don ors (p < 0.05). The results indicate that spermatozoa surviving in extra-ep ididymal sites are more likely to possess DNA and chromatin abnormalities t han those present in the testes and epididymis. These changes may partly ex plain the depletion of cell viability and fertilizing capacity of extra-epi didymal spermatozoa which has been reported previously.