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Induction of hyperactivated motility in equine sperm with ammonium chloride

Kelly Sulik, Young-Ho Choi, Kristin Rolke, Dickson Varner and Katrin HinrichsDepartment of Veterinary Physiology and Pharmacology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University,
College Station, TX 77843-4466, USA

Structured Abstract


This study was conducted to determine whether increased intracellular pH, as induced by the weak cell-permeant base ammonium chloride, is associated with hyperactivated motility in equine sperm.

Animals or Sample Population:

Equine semen samples from stallions owned by Texas A&M University and bovine semen samples generously donated by Ultimate Genetics of Wheelock, Texas, were used in this study.


Studies were conducted to define an effective medium for supporting multiple centrifugations of equine sperm without use of a complex solution such as milk. Sperm suspended in the defined medium were then exposed to varying concentrations of ammonium chloride and motility parameters were assessed using computer-assisted sperm analysis.


Equine sperm in initial studies were rendered largely immotile after centrifugation and resuspension in the medium described by Marquez and Suarez. Replacing bovine serum albumin with 0.02% polyvinyl alcohol allowed equine sperm to remain motile after being washed. Studies performed in the modified medium showed that ammonium chloride caused maximally increased curvilinear velocity of bovine sperm at a concentration of 50mM, and maximally increased amplitude of lateral head movement at a concentration of 25 mM, while the maximum values for these parameters were achieved at a concentration of 5 mM in equine sperm.

Conclusions and Clinical Relevance:

Equine sperm become hyperactivated at a lower concentration of ammonium chloride than do bovine sperm. The information from this study will aid in clarifying the physiology behind the difficulties in performing equine in vitro fertilization, and may help to make equine in vitro fertilization a realistic option for the equine industry.