Effect of dextrans on cryopreservation of goat cauda epididymal spermatozoa using a chemically defined medium

Abstract

Experiments were carried out to investigate the cryoprotecting potential of dextrans (ranging from 10 to 2000 kDa) using a synthetic model system developed recently in this laboratory. Goat spermatozoa from the cauda epididymidis were extracted in a chemically defined medium (modified Ringer's solution) and assayed for motility using a phase-contrast microscope. The sperm cells were subjected to a freezing protocol in a computer-controlled biofreezer (cooling at 0.25 degrees C min(-1) to 5 degrees C; 5 degrees C min(-1) to -20 degrees C; 20 degrees C min(-1) to -100 degrees C) and plunged into liquid nitrogen. The frozen cells were thawed rapidly at 37 degrees C in a thermostatic waterbath. In the absence of dextran, all the spermatozoa lost their motility. The cryoprotecting efficacy of each dextran was found to be biphasic in nature. Initially, as the concentration of dextran was increased, the recovery of sperm motility also increased and reached an optimum value; however, with further increases in dextran concentration, the recovery of motility decreased sharply. Of all the sugar polymers tested, 10 kDa dextran showed the highest cryoprotecting efficacy, whereas the 2000 kDa sugar polymer was the least active. Dextrans of 10, 40, 73, 173, 252, 500 and 2000 kDa offered maximum cryorecovery of forward motility to the extent of approximately 23%, 21%, 19%, 18%, 16%, 15% and 8%, respectively. Optimum concentrations of these dextrans for cryoprotection of sperm motility were 8.42, 2.50, 1.09, 0.37, 0.31, 0.10 and 0.04 mmol l(-1), respectively. It thus appears that each dextran has a characteristic cryoprotection profile. The data show that the cryoprotecting efficacy and optimum cryoprotecting concentrations of dextrans are inversely related to their molecular mass. Dextran also served as a significant cryoprotectant in the presence of glycerol (0.87 mol l(-1)) and dimethyl sulphoxide (0.76 mol l(-1)), which are well known cryoprotectants; the action of the combined cryoprotectants was almost additive. The presence of glycerol or glycerol plus dimethyl sulphoxide caused a significant reduction (from 8.42 to 6.27 mmol l(-1)) in the optimum concentration of dextran. In the presence of the three cryoprotectants, recovery of sperm motility was as high as 58% (forward motility) and 60% (total motility).

Cryopreservation of domestic animal sperm cells

“…Therefore, non penetrating cryoprotectant may alter the plasma membrane, or act as a solute, lowering the freezing temperature of the medium and decreasing the extracellular ice formation (Amman 1999; Kundu et al 2002).…”

Effect of low-density lipoproteins, spermatozoa concentration and glycerol on functional and motility parameters of bull spermatozoa during storage at 4 °C

“…12 Therefore, they may protect the plasma membrane or act as a solute, lowering the freezing temperature of the medium and decreasing extracellular ice formation. 13,14 Male animals can be classified as 'good or bad freezers' depending on the aptitude of their semen to support freezing with little cryodamage. 3 Often the selection of the reproductive bulls is based on the capacity of semen to support freezing.…”

Liquid Storage of Goat Semen in Chemically Defined Extenders

“…2003; Paulenz et al. 2005); so are the reports on cryopreservation of goat spermatozoa in such chemically defined media (Kundu et al. 2000, 2002; Khalifa and El‐Saidy 2006).…”