Osmotic tolerance of mouse spermatozoa from various genetic backgrounds: acrosome integrity, membrane integrity, and maintenance of motility

All cells have an intrinsic biophysical property related to their ability to undergo osmotically driven volume changes. This project is of fundamental importance to our understanding of the basic cryobiology of mouse spermatozoa. The objectives of this study were to determine the osmotic tolerance limits for (1) motility, (2) acrosome integrity, and (3) membrane integrity of mouse spermatozoa from multiple genetic backgrounds including: C57BL/6, BALB/c, FVB, C3H, 129/SVS2 hsd B6C3F1, CB6F1, and ICR. The maintenance of acrosomal and plasma membrane integrity was not affected by genetic background (p=0.13), however, there was an interaction between genetic background and osmolality. In addition, acrosome and plasma membrane integrity was highly correlated within each strain (p<0.01). In contrast to acrosome and plasma membrane integrity, the motility of spermatozoa from different genetic backgrounds fell sharply on both sides of isosmolality, both with and without return to isosmotic conditions. Exposure to hyposmotic conditions caused morphological changes in the spermatozoa, which inhibited motility. However, this morphological change was not reversible in all cases when returned to isosmotic conditions. The ability to maintain motility in an anisosmotic media was affected by genetic background, osmolality as well as the interaction between genetic background and osmolality (p<0.05). In conclusion, mice with different genetic backgrounds appear to have similar tolerance to osmotic changes in terms of sperm acrosome and plasma membrane integrity; however, the ability to maintain motility differs between genetic backgrounds.