[The effect of the period of cryopreservative storage on the cryosurvival of human spermatozoa].

Objectives: To study the effect of cryopreservative period on the cryosurvival of human spermatozoa and find out the optimal recovery time of cryopreservation.

Methods: Eighty-eight semen samples were collected from normal donors and divided randomly into 5 groups according to the period of cryopreservative storage (1 d, 7 d, 30 d, 180 d, 300 d) in liquid nitrogen after being frozen by the programized, three-step freezing method. Fresh and frozen-thawed semen were examined by the routine analysis of semen and then the sperm recovery rate were calculated.

Results: There were no significant differences in sperm recovery rate between group I and the others (P > 0.05). The period of cryopreservative storage in liquid nitrogen had no correlation with the cryosurvival of human spermatozoa (r = 0.05, P > 0.05).

Conclusions: It was indicated that freezing-thawing after 24 h would be helpful to the screening of semen donors in batches for donor insemination of human sperm bank.