CHROMATIN CONDENSATION IN CAT SPERMATOZOA DURING EPIDIDYMAL TRANSIT AS STUDIED BY ANILINE BLUE AND ACRIDINE-ORANGE STAINING

Chromatin stability and DNA-resistance to acidic denaturation was evaluated by acidic aniline blue and acridine orange staining of cat sperm from different regions of the epididymis. The results were related to conventional sperm parameters. The percentage of aniline blue-stained spermatozoa (persisting histones) decreased significantly from the caput to the cauda region (31.8% and 7.8%, respectively; P < 0.0001). The percentage of stained heads of cauda sperm was much lower in populations of morphologically normal forms than in those with abnormal forms (4.1% and 13.8%, respectively, P < 0.0001). Among spermatozoa with abnormalities, the percentage of stained heads was significantly higher in cells with head abnormalities than in sperm with only tail abnormalities (87.1% and 10.3%, respectively; P > 0.0001). With acridine orange fluorescence staining, 86.5% of cauda epididymal sperm were found with well-condensed chromatin, stabile against acid-induced denaturation. Chromatin stability increased significantly from the caput epididymal region (51.1%) to the cauda epididymal region (86.5%). The percentage of cauda epididymal sperm with normal condensed chromatin was neither linked to testicular sperm count, motility nor to age of the cats. The parameter of chromatin condensation and stability can be a valuable index of sperm quality, reflecting the possible disorders of spermatogenesis and epididymal sperm maturation, frequently observed in feline species.