Evaluation of sperm membrane functionality during epididymal transit in red-rumped agouti (Dasyprocta leporina)

We studied the sperm membrane functionality through the epididymal transit by comparing different hypoosmotic solutions and verifying possible associations among osmotic response and functional parameters of sperm in red-rumped agouti (Dasyprocta leporina). For this purpose, epidydimal sperm from six sexually mature male agoutis were collected via flotation. Then, analyses of sperm parameters and hypoosmotic swelling test using different hypoosmotic solutions (0 mOsm/l, 50 mOsm/l, and 200 mOsm/l) in different regions of the epididymis (caput, corpus, and cauda) were performed. There was an increase (P < 0.05) in the values for sperm concentration, total number of sperm recovered, total and progressive motility, average path velocity, straightline velocity, curvilinear velocity, rapid and medium subpopulations following the caput-corpus-cauda direction. Regardless the hypoosmotic solution, agouti sperm membrane presented similar functional integrity in all the epididymal regions. Moreover, the highest (P < 0.05) osmotic responses were reached at the use of 50 mOsm/l solution in comparison to 0 mOsm/l and 200 mOsm/l for all the regions. Significant correlations among osmotic response and some sperm kinetic parameters were especially observed in epidydimal caput, while no correlations were found in the region of the cauda. In summary, red-rumped agouti sperm present similar membrane functionality during epidydimal transit, but there are evident correlations among such functionality and sperm kinetic parameters, especially at the caput region. Moreover, we indicate the use of a 50 mOsm/l hypoosmotic solution for the analysis of this parameter through the hypoosmotic swelling test.