The Effect of Calcium Ions on Cell Volume and Motility of Bovine Spermatozoa

Abstract

Summary

Ca²⁺ was added to a buffered medium containing various combinations of K⁺, fructose, CN^-, ouabain, and BSA. Constant osmolarity, pH, and temperature of the incubation media were maintained. Without K⁺ in the medium, Ca²⁺ limited the duration of rapid swelling of spermatozoa by causing early onset of shrinkage to about 90% of initial cell volume. Shrinkage occurred sooner as the Ca²⁺ level increased, and was associated with a fuzzy microscopic appearance of the sperm cells. Addition of 2.25 to 3.0 mM K⁺, and to a lesser extent 1.0 mM of fructose, delayed the onset of swelling and subsequent shrinkage associated with Ca²⁺ alone. This delay also was observed in a variety of media which promoted good sperm motility. BSA was able to counteract the effects of Ca²⁺, but this was abolished by addition of CN^-. Fructose overcame the CN^- effect, indicating that the process is energy related. It appears likely that Ca²⁺ enters the cell only after energy sources are depleted, and its presence there causes structural and permeability changes in spermatozoa.