CRYOPRESERVATION OF MOUSE SPERMATOZOA .2. RELATIONSHIP BETWEEN SURVIVAL AFTER CRYOPRESERVATION AND OSMOTIC TOLERANCE OF SPERMATOZOA FROM 3 STRAINS OF MICE

A procedure to cryopreserve mouse spermatozoa has been derived to bank the genetics of valuable strains of mice in a practical way. The prim ary objective of this study was to apply the cryopreservation method d eveloped for spermatozoa of strain B6D2F1 to those of strains 129/J an d C57BL6/J. Using the capability of spermatozoa to fertilize oocytes i n vitro as the criteron of survival, we found differences in survival after cryopreservation among the three strains. Blastocysts were obtai ned after in vitro fertilization of oocytes with frozen spermatozoa fr om B6D2F1 (51%) and 129/J (12%); none was obtained from C57BL6/J. Tran sfer of embryos into recipients resulted in the birth of 69 live pups from 164 embryos produced with frozen B6D2F1 spermatozoa and 11 pups f rom 35 embryos produced with 129/J spermatozoa. To seek an explanation of these differences among the three strains, spermatozoa were expose d to anisotonic solutions ranging from 5 to 3200 mOsm; viability of sp ermatozoa was assessed by a double stain using flow cytometry. Mouse s permatozoa tolerated exposure to solutions of osmolalities between 200 and 400 mOsm, but were damaged when exposed to solutions exceeding th is range. Spermatozoa from C57BL6/J were the most sensitive: 20, 35, a nd 40% of C57BL6/J, 129/J, and B6D2F1 spermatozoa survived exposure to an 800 mOsm solution, respectively. This study suggests that there is a genetic basis for sensitivity of mouse spermatozoa to osmotic shock and freezing injury. Nevertheless, the birth of the pups produced wit h frozen spermatozoa from 129/J as well as with spermatozoa from B6D2F 1 mice indicates that cryopreservation of spermatozoa can be used to p resence the genetics of valuable strains of mice. (C) 1997 Academic Pr ess.