Effect of male reproductive tract fluids and proteins on the metabolism and motility of ram spermatozoa.

Cauda epididymal fluid (CEF) greatly stimulated the oxygen uptake of washed ejaculated ram spermatozoa; the effect was evident within 1 h and persisted over the 8 h of the experiment. The stimulus was comparable to that produced by 10 mM glucose and the effects were not additive, that is, CEF and CEF plus glucose elicited about the same oxygen uptake. This suggested that CEF suppressed the oxidation of added glucose and this was confirmed by measuring the amount of glucose oxidized in the presence and absence of CEF. Cauda epididymal fluid improved the motility of washed ram spermatozoa but it was somewhat less than that produced by glucose and usually only became evident after about 6 h or incubation. Electrophoretic analysis of cauda epididymal spermatozoa incubated in radioiodinated CEF showed that these cells absorb fluid components in the zone 82 to 56 kD. However, a molecular weight fraction less than 5 kD obtained by passing CEF through a Sephadex G-25 column, was not effective in stimulating the oxygen uptake of ram spermatozoa. The effects of CEF on the metabolism of ram spermatozoa could be mimicked by 2.5-4.0 mg/ml bovine serum albumin (BSA). Stimulation of oxygen uptake was apparent within 1 h and persisted over the 8 h of the experiment. As with CEF, stimulation of oxygen uptake by BAS was less than with 10 mM glucose but the effects were not additive. Like CEF, BSA reduced the amount of glucose oxidized. Bovine serum albumin also improved the motility of ram spermatozoa over 8 h. After passage through Sephadex G-25 to remove any low molecular weight contaminants (less than 5 kD), BSA was still effective in stimulating the oxygen uptake of spermatozoa over 4 h. Ram blood plasma and especially ram seminal plasma were also effective after passage through the Sephadex. Human serum albumin (HSA) was as effective as BSA in stimulating the oxygen uptake of ram spermatozoa but defatting decreases its effectiveness. The motility score of the spermatozoa was also adversely affected by this treatment. It is concluded that the stimulating effects of CEF and of the other fluids and proteins are due to substrates, at least some of which are present as or associated with macromolecules.