Effects of ouabain on the response to osmotic changes in dog and boar spermatozoa

Although there is much information on the response of spermatozoa from different species to osmotic changes, little has been reported about the mechanism/s by which spermatozoa react to similar changes in the osmotic pressure of the medium. In this study we examine the effect of inhibition of Na+/K+, ouabain-sensitive ATP-ase on the response of canine and porcine spermatozoa when they are incubated in hypoosmotic and hyperosmotic media. The presence of ouabain slightly decreased the percentages of total and progressive motility, and increased the percentages of altered acrosomes (from 13.0 ± 0.3% to 17.2 ± 0.4% in the presence of 10-4 M ouabain) and, specially, swollen tails (from 0.6 ± 0.1% to 5.9 ± 0.2% in the presence of 10-4 M of ouabain) in fresh dog semen, although it did not affect these parameters in boar semen samples. Moreover, ouabain increased the percentage of both altered acrosomes and swollen tails in canine spermatozoa incubated in 100 mOsm and in 900 mOsm media at concentrations higher than 10-5 M and 10-7 M, respectively. The percentage of viability of canine spermatozoa was not modified by ouabain after incubation in 100, 300 or 900 mOsm media. Furthermore, ouabain did not significantly affect boar spermatozoa incubated in 100, 300 or 900 mOsm media. Although ouabain induced a significant decrease in L-lactate production in canine spermatozoa in an isoosmotic medium (from 4.7 ± 0.4 μmol/mg protein × 60 min to 2.6 ± 0.3 μmol/mg protein × 60 min in the presence of 10-4 M ouabain), there was no significant effect on L-lactate production in boar spermatozoa. These results indicate that while dog spermatozoa acted against changes in the osmotic pressure by a mechanism(s) related to Na+/K+, ouabain-sensitive ATP-ase, boar spermatozoa reacted to some mechanism(s) not related to ionic pumps.