Availability of sperm examination for male reproductive toxicities in rats treated with boric acid.

Sperm morphological examination, computer-assisted sperm analysis (CASA) and histopathologic examination of the testis and epididymis were performed for male rats treated orally with boric acid for 3 weeks at dosage levels of 50, 150 and 500 mg/kg/day, and treated males were mated with untreated females. None of the males treated with 500 mg/kg/day could impregnate untreated females. The fertility index showed a tendency to decrease in males treated with 150 mg/kg/day. At necropsy, the pre-implantation loss rate in females mated with males treated with 150 mg/kg/day was higher than the control values. Upon epididymal sperm analysis using the CASA system, all parameters including the number of sperm and sperm motions were found to be affected in males treated with 500 mg/kg/day, and the number of sperm, percent motile, velocities and amplitude of lateral head displacement (ALH) were affected in males treated with 150 mg/kg/day. Upon sperm morphological examination, head and tail abnormalities were observed in males treated with 150 and 500 mg/kg/day. In the histopathological examination, atrophy of the seminiferous tubules and multinucleated giant cells in the testes were observed in males treated with 500 mg/kg/day.