Ma. Alvarenga et al., Acrosomal ultrastructure of stallion spermatozoa cryopreserved with ethylene glycol using two packaging systems, EQUINE V J, 32(6), 2000, pp. 541-545
The present experiments aimed to examine the substitution of glycerol (G) b
y ethylene glycol (E) as a cryoprotective agent for stallion spermatozoa. T
wo different ethylene glycol concentrations (5% and 10%) and also the assoc
iation of glycerol (2%) and ethylene glycol (3%) (E/G) were studied (Experi
ment 1). In Experiment 2, two packing systems (0.5 x 4.0 ml) were evaluated
using both cryoprotectors. In both experiments, the sperm membrane integri
ty after freezing was evaluated using transmission electron microscopy. The
mean post-thaw motility was 34.25, 36.5, 29.25 and 34.75% for G5%, E5%, E1
0% and E/G, respectively. It was observed that the percentage of motile spe
rmatozoa was significantly smaller (P<0.05) when semen was processed with E
10%. A decrease in the acrosome integrity was observed in frozen thawed spe
rmatozoa from all treated groups. It was observed that 28.0, 22.5, 25.5 and
22.5 % of the sperm cells had a normal acrosome following freezing with G5
%, E5%, E10% and E/G, respectively. Undulation of the outer acrosomal membr
ane, acrosomal swelling and loss of acrosomal content density and homogenei
ty were the most evident ultrastructural alterations observed. In Experimen
t 2, the post-thaw motility was higher (P<0.05) for sperm frozen in 0.5 ml
straws than in 4.0 mi straws, regardless of the cryoprotector used. The ult
rastructural evaluation showed 26.7 and 16.0% of intact acrosomes for sperm
frozen in 0.5 ml and 4.0 ml straws, respectively. We concluded that ethyle
ne glycol has similar cryoprotective properties to glycerol and that utilis
ation of 0.5 ml straws improved the ability of horse sperm cells to withsta
nd damage after the cryopreservation process.