THE HYPOOSMOTIC SWELLING TEST - ITS EMPLOYMENT AS AN ASSAY TO EVALUATE THE FUNCTIONAL INTEGRITY OF THE FROZEN-THAWED BOVINE SPERM MEMBRANE

The objective of this study was to determine the effectiveness of the hypoosmotic swelling (HOS) test together with the supravital test as a means of evaluating the functional integrity of frozen-thawed bovine sperm membrane. A solution consisting of equal parts of fructose and s odium citrate was prepared and the osmolality varied from 50 to 300 mO sm/L. From these various solutions under study, the 100 mOsm/L solutio n resulted in a maximal number of clearly identifiable swollen spermat ozoa. The results from the supravital test indicated that the HOS solu tion preserved the integrity and prevented excessive lysis of the sper m membrane during the assay. A good correlation was found between the percentage of motile spermatozoa and spermatozoa that reacted to the H OS test (r=0.73) and between the percentage of sperm with intact membr anes and HOS reactive sperm (r=0.81). Spermatozoa showing swelling of the entire tail region accounted for more than 60% of the total swelli ng for the HOS solution at 100 mOsm/L. The results obtained in this st udy indicate that frozen-thawed bovine spermatozoa did react to the HO S test. This technique could prove useful in studies involving the fun ction of the sperm membrane and could possibly predict the sperm's abi lity to fertilize.