Maturation of hamster epididymal sperm motility and influence of the thiol status of hamster and rat spermatozoa on their motility patterns

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Abstract
A method for objective quantification of hamster sperm movement parameters as an indicator of maturation along the epididymis was established using a computerised system. Analysis of spermatozoa released into medium from five epididymal regions showed that the most drastic increases in percentage motility and curvilinear velocity (VCL) occurred from the distal corpus to the beginning of the proximal cauda and in straight‐line velocity (VSL) from the beginning to a more distal site within the proximal cauda region. Both high osmolarity (400 mOsm/kg) and the thiol‐oxidising agent diamide (10 μM) increased flagellar straightness of distal corpus spermatozoa, but VSL was increased only with the latter. The thiol‐reducing agent dithiothreitol (DTT, 1mM) stimulated and maintained percentage motility and velocities of spermatozoa from the caput, stimulated only percentage motility of distal corpus sperm, but decreased velocities of those from the proximal cauda in prolonged incubation. In rats, diamide increased path straightness but not velocities of caput spermatozoa and yet caused immotility within 15 min, whereas DTT prolonged the maintenance of in vitro motility. The slight increases in kinematic parameters in the presence of DTT were enhanced by a 2‐min preincubation with diamide. The finding that the effects of DTT and diamide were not compensatory suggests that the influence of the SH/S‐S status on sperm movement is multifaceted, with decreasing sensitivity to stimulation upon sperm maturation.