Comparison of cryoprotective effects of iodixanol, trehalose and cysteamine on ram semen

Abstract

This study was conducted to improve cryosurvival of electroejaculated (EE) ram semen in the presence of iodixanol (OptiPrep (TM)), trehalose or cysteamine. A tris-based extender was used to prepare 12 extenders containing OptiPrep (TM) (Op), trehalose (Tr) or cysteamine (Cy) alone, or different combinations of these compounds. Extenders were designated as follows: Tris (control), Op1.25 (1.25% Op, v/v), Op2.5 (2.5% Op, v/v), Op5 (5% Op, v/v), Tr50 (50 mM Tr), Tr100 (100 mM Tr), Cy (5 mM Cy), OpTr (2.5% Op and 100 mM Tr), OpCy (2.5% Op and 5 mM Cy), TrCy (100 mM Tr and 5 mM Cy), OpTrCy1 (2.5% Op, 100 mM Tr and 5 mM Cy) and OpTrCy2 (1.25% Op, 50 mM Tr and 2.5 mM Cy).

A two-step dilution was used and glycerol was added at 5 degrees C in the second step. Diluted samples were equilibrated for 1 h, loaded in 0.25 mL straws and frozen in a programmable freezing machine. Supplementation of 5% OptiPrep (TM) significantly protected post-thaw progressive motility, membrane integrity, acrosomal integrity and morphological damages. Trehalose supplementation protected membrane integrity of ram sperm; however, it did not help post-thaw motility and morphology. Supplementation of 5 mM cysteamine had detrimental effect on cryosurvival of EE ram semen. These results demonstrate that the supplementation of iodixanol increases the cryosurvival of EE ram semen in a dose-dependent manner. (c) 2013 Elsevier B.V. All rights reserved.