EFFECT OF PREFREEZING EQUILIBRATION AND POSTTHAWING CENTRIFUGATION ONTHE FERTILIZING-CAPACITY OF FROZEN MOUSE EPIDIDYMAL SPERMATOZOA

Effect of pre-freezing equilibration and post-thawing low speed centri fugation on the survival of frozen-thawed mouse epididymal spermatozoa was investigated. Pre-freezing equilibration for 1 or 5 h at 5-degree s-C decreased the in vitro fertilization (IVF) rate of frozen-thawed s permatozoa. High IVF rates (71 - 85 %) from spermatozoa of ICR, C3H/He N and BALB/c and moderate IVF rates (53 and 58 %) from C57BL/6N and SA M-P/6 spermatozoa, respectively, were obtained when they were immediat ely frozen, thawed and subsequently subjected to the centrifugation (2 ,000 g for 1 min) prior to IVF.