The purpose of this study was to evaluate the age-dependent response of testicular toxicity and the mechanism of di(2-ethylhexyl) phthalate (DEHP) induced testicular toxicity.

DEHP was administered orally in doses of 0, 1.0 and 2.0 g/kg/day, for 7 days, to 3, 6 and 9 week-old Sprague-Dawley rats. Testicular weight and sperm head counts, plasma level of DEHP, mono(2-ethylhexyl) phthalate (MEHP) and testicular lipid peroxidation were measured. Histopathological changes in the testis were observed.

Reductions in weight gains, and relative testis weights, were observed in the 3 week-old rats in a dose-dependent manner, but not in the 6 and 9 week-old rats, compared to those of the control rats. Sperm head counts were decreased in the 6 week-old rats exposed to 2.0 g/kg/day, but not in the 9 week-old rats. Testicular atrophy and significant size reduction of the seminiferous tubule were observed in a dose-dependent manner in the 3 week-old rats. The plasma concentrations of MEHP were higher than those of DEHP, with these levels being most elevated in the younger rats. Lipid peroxidation, following exposed to DEHP, was increased in a dose-dependent manner in the 3 week-old, but with no changes in the 6 and 9 week-old rats.

Our results suggest the age related difference observed in the testicular response to the oral administration of DEHP may be due to the metabolism, and that oxidative stress may be related to the mechanism of DEHP induced testicular toxicity.