MOTILITY OF CRYOPRESERVED MOUSE SPERMATOZOA AFFECTED BY TEMPERATURE OF COLLECTION AND RATE OF THAWING

In an attempt to optimize a method of cryopreserving spermazoa from mi ce bearing mutations, we investigated the effect on motility of temper ature for the collection of mouse sperm and the rate of thawing after freezing. Comparison among samples of sperm collected from both the ca udae epididymides and vas deferens placed directly in a cryoprotectant of 3% skim milk and 18% raffinose equilibrated at 37, 23, and 3 degre es C showed no difference in the number of viable sperm harvested. Con centration and motility was highest after collection at 37 degrees C ( 22.3 x 10(6) sperm/ml with 80% motility) combined with rapid thawing a t 37 degrees C (2.9 x 10(6) sperm/ml with 84% motility in the swim-up fraction). The fertilization capacity of sperm collected and thawed at 37 degrees C was analyzed in vitro and no difference was observed bet ween the cryopreserved sperm and the control (91 and 89%, respectively ). Transfer of in vitro fertilized embryos to pseudopregnant recipient s resulted in 37% implantation at Day 10 of pregnancy and 38% live bir ths at term. (C) 1997 Academic Press.