Alvarez-Rodriguez M, Vicente-Carrillo A and Rodriguez-Martinez H
Objective: Despite the use of high proportions of the chemically undefined lipoprotein/phospholipid-rich egg-yolk in extenders, boar sperm are highly sensitive to cooling, which induces ROS generation and disrupts the plasma membrane. Here, we studied whether replacement of hen egg-yolk by commercially defined lecithin phospholipids, derived from egg (LPGE: phosphatidyl glycerol, LPCE: phosphatidyl choline) or soybean (LPCS: phosphatidyl choline), could individually ameliorate such oxidative effects during cryopreservation of ejaculated (spermrich fraction, SRF) or of cauda-epididymal sperm, retrieved post-mortem from the same males.
Methods: A conventional extender (lactose buffer, with 20% egg-yolk, 0.5% OEP and 3% glycerol) was used as control. Cryodamage was assessed as loss of sperm motility, membrane and acrosome intactness, early membrane destabilization changes, mitochondrial potential, superoxide and ROS production, to finally determine lipid peroxidation (LPO) using specific probes.
Results and conclusion: In general, the exogenous phospholipids assayed were unable of maintaining neither sperm motility nor viability post-thaw compared to controls, owing to increased ROS production and lipid peroxidation. In our study, mitochondrial superoxide production resulted in very high levels for all groups, whereas both ROS production and lipid peroxidation were reduced in the control group, containing emulsified hen egg yolk. Further studies using various dosage and combination of LPCS should be followed for their eventual protective effect.
