Semen quality and chromatin condensation in domestic cat sperm during passage through the epididymis

Abstract

The objectives were to identify and quantify changes occurring in cat sperm as they pass through the epididymis, vas deferens and ejaculate. Cat epididymides obtained by orchidectomy were divided into six regions (1 to 6) and sperm cells were released by mincing each epididymal region. The semen quality was assessed by light microscopy and the sperm chromatin condensation was measured by flow cytometry. The sperm motility was minimal in region 1 and increased significantly (p < 0.05) when the sperm passed from this region, with maximum motility reached in region 6, the vas deferens and ejaculate. Progressive motility and the percentage of sperm with normal morphology increased during epididymal transit. The most prevalent defects in abnormal spermatozoa were found in the tail. The mean degree of maturation (± standard error of the mean) of sperm chromatin condensation was 72.9 ± 9.4% in region 1 and was significantly (p < 0.05) increased in region 3 (94.4 ± 2.6%). Chromatin condensation or decondensation processes were studied further in cat epididymides (four portions: initial segment, caput, corpus and cauda) by incubating sperm with alkaline phosphatase (AP) or dithiothreitol (DTT), respectively, followed by staining with propidium iodide and analysis by flow cytometry. After AP treatment, the fluorescence intensity approximated that found in the initial segment. The DTT treatment significantly (p < 0.05) increased the fluorescence of the chromatin condensation in all parts, except the initial segment. Cat sperm chromatin was shown to undergo condensation during passage through the epididymis and the condensation process was reversed by reducing disulfide to sulfhydryl bonds or promoted by dephosphorylation.