Testicular spermatid and epididymal sperm head counts as an indicator for reproductive toxicity in rats.

The testes of rats were exposed to a single soft x-ray irradiation at levels of 10, 25 and 63 Gy. Testicular and cauda epididymal weights and their sperm counts were decreased at 7 weeks after the irradiation. Histologically, there was an evidence of interrupted spermatogenesis dose-dependently. Animal mating trails, in which irradiated males were mated with untreated females revealed a slight increase in early stage of postimplantation loss at as low as 10 Gy. There were increases in preimplantation and early stage of postimplantation losses in the group of irradiated at 25 Gy. Infertility occurred in irradiated males at 63 Gy. The effects of irradiation were more severe on the sperm count parameters than on reproductive organ weights, histological examination and reproductive status. The testicular spermatid and epididymal sperm head counts are considered to be useful indicators to detect quantitatively the adverse effects on spermatogenesis.