ABSTRACT
Since bull fertility prediction remains challenging, the identification of potential fertility markers is important considering the economic benefits to the livestock industry. The main goal of this study was to determine the Na/K-ATPase activity and expression in thawed sperm of high (HF)- and low-fertility (LF) Angus bulls. Samples from three different batches/bulls with HF (n = 4) and LF (n = 4) were used. The Na/K-ATPase activity was determined after thawing, whereas sperm kinematics, membrane integrity, and expression of Na/K-ATPase on sperm surface were evaluated immediately post-thaw and after 120 minutes of incubation. Within the same incubation time, there was no difference on sperm membrane integrity, kinematics, and the expression of Na/K-ATPase on the sperm surface between HF and LF bulls. Kinematic parameters of LIN and VCL were not influenced by incubation time in samples from HF and LF, respectively. A tendency (P = 0.06) of higher Na/K-ATPase enzymatic activity for sperm of HF bulls compared to LF bulls was observed (0.49 ± 0.07 and 0.32 ± 0.06, respectively). In conclusion, Na/K-ATPase activity and expression in thawed sperm from Angus bulls are not related to the fertility index after fixed-time artificial insemination. However, sperm kinematics related to hyperactivation might indicate higher sperm cryotolerance for HF bulls.
ABSTRACT
Although equine blastocysts ≤ 300 µm in diameter can be successfully vitrified, larger equine blastocysts are not good candidates for cryopreservation. As Na+, K+-ATPase is involved in maintaining blastocyst expansion, perhaps inhibition of this enzyme would be a viable method of reducing blastocyst diameter prior to cryopreservation. Objectives were to evaluate effects of ouabain-induced inhibition of Na+, K+-ATPase in equine blastocysts. Sixteen mares were ultrasonographically monitored, given deslorelin acetate to induce ovulation, and inseminated. Embryos (D7 and D9) were harvested and Na+, K+-ATPase inhibited for 1 or 6 h by exposure to 10-6 M ouabain, either natural ouabain or conjugated to fluorescein (OuabainFL), during incubation at 37° C. Evaluations included morphometric characteristics (bright field microscopy) and viability (Hoescht 33342 + propidium iodide). Blastocysts incubated for 6 h in Holding medium + ouabain (n=3) had, on average, a 45.7% reduction in diameter, with adverse morphologic features and no re-expansion after subsequent incubation in Holding medium for 12 h. In subsequent studies, even a 1-h exposure to Ouabain or OuabainFL, caused similar reductions, namely 38.7 ± 6.7% (n=5) and 33.6 ± 3.3% (n=7) for D7 and D9 blastocysts, respectively. Ouabain binding was confirmed after OuabainFL exposition and all embryos (n=12) lost viability. We concluded that Na+, K+-ATPase inhibition with ouabain caused death of equine blastocysts and therefore was not a viable method of reducing blastocyst size prior to cryopreservation.
