The ultrastructure and metabolism of ejaculated tammar wallaby sperm are impaired by swim-up procedures when compared with sperm from the cauda epididymidis

The metabolism, rate of intracellular accumulation of sugars, motility and ultrastructure of ejaculated tammar sperm were impaired by swim-up into art ificial media, particularly when the cells were subsequently exposed to N-a cetyl-D-glucosamine (NAG). The inclusion of hyaluronate, serum albumin, cat alase or Desferal in swim-up media helped prevent deterioration of sperm mo tility, but failed to prevent detrimental NAG-induced metabolic and ultrast ructural changes. However, the sperm were unavoidably diluted during swim-u p into artificial media acid their behavioural properties were modified by dilution. Thus, sperm collected from the cauda epididymidis were immotile a nd their rate of oxygen uptake was low in undiluted caudal epididymal semen (CES). Nevertheless, these sperm were viable, and vigorous motility was in duced by 5- to SD-fold dilution in Krebs-Ringer phosphate (KRP). Sperm resp iration also dramatically increased with moderate dilution (5- or 15-fold) in KRP,but decreased again at higher rates (50-fold). This suggested that m otility and the metabolic properties of tammar sperm are modified both by d ilution and on leaving the suppressing conditions of the epididymis. Dilute d tammar epididymal sperm also displayed a Pasteur effect, but rapidly lost capacity for motility in an oxygen-depleted atmosphere, it was concluded t hat swim-up procedures compromise ejaculated tammar sperm by promoting dilu tion-induced changes. This may alter the permeability of the membrane with loss of the enzymes that process the ammonia generated during the metabolis m of NAG in seminal plasma. Subsequent exposure to NAG further promotes ult rastructural damage culminating in loss of viability.