INDUCTION OF MICRONUCLEI IN HUMAN SPERM-HAMSTER EGG HYBRIDS AT THE 2-CELL STAGE AFTER IN-VITRO GAMMA-IRRADIATION OF HUMAN SPERMATOZOA

The efficiency of the micronucleus test to assess radiation-induced ch romosomal damage in human spermatozoa has been investigated. Micronucl ei were scored in human sperm-hamster egg hybrids at the two-cell stag e, after exposure of human spermatozoa to in vitro gamma-rays at doses of 0.00, 0.10, 0.25, 0.50, 1.00, 2.00, and 4.00 Gy. The relationship between the yield of micronuclei per two-cell stage as well as the per centage of two-cell stages with micronuclei and the different doses of irradiation were fitted to linear equations. To evaluate whether scor ing micronuclei is useful for the quantification of chromosomal damage occurring in human spermatozoa, induced micronuclei at the different doses of sperm irradiation were compared to the induction of breaks an d fragments in sperm-derived chromosomes. After interspecific fertiliz ation of zone-free hamster oocytes by irradiated spermatozoa, a total of 699 fertilized eggs at the two-cell stage and a total of 387 sperm- derived complements were analyzed. The incidence of fertilized eggs wi th micronuclei at the two-cell stage coincided well with the incidence of sperm-derived chromosome breaks and fragments (e.g., 8.9% vs. 6.7% in the 0.25 Gy group and 52.8% vs. 58.6% in the 4.00 Gy group). A sim ilar correlation was found between the number of micronuclei per two-c ell stage and the number of breaks and fragments per sperm complement (0.09 vs. 0.07 in the 0.25 Gy group and 0.71 vs. 0.81 in the 4.00 Gy g roup). The results show that this test system con be used for the quan tification of spontaneous or induced chromosomal damage in human sperm atozoa. (C) 1995 Wiley-Liss, Inc.