Sex-specific accumulation of silver nanoparticles in rat kidneys is not ovarian hormone regulated but elimination limited

Abstract

Preferential Ag deposition in female kidneys has been reported in subacute and subchronic oral gavage and inhalation studies of various sizes of silver nanoparticles (AgNPs). In these in vivo animal studies, female kidneys were shown to accumulate 3–4 times more silver than male kidneys. The current 28-day oral gavage study of AgNPs administered to ovariectomized female rats investigated the effect of sex-dependent hormones. Ovariectomized rats were allowed to recover for 14 days, then AgNPs (60 nm) were administered by gavage for 28 days based on 500 mg/kg body weight. After this subacute oral exposure, the rats were sacrificed and the Ag content in the kidneys was measured using an atomic absorption spectrophotometer. No statistically significant difference was noted in the Ag content in the kidneys among the AgNP administered, AgNP administered sham, and AgNP administered ovariectomized rats, although the female kidneys showed a statistically significant higher accumulation of Ag than the male kidneys. Reanalysis of the clearance of Ag accumulated in the kidneys showed 2 different phases; fast (T1/210.4 days) and slow (T1/2 61.9 days) for males, while the clearance of females showed (T1/2 20.8 days) and slow (T1/2 154 days). The higher accumulation of Ag in female kidneys is due to slower clearance of Ag in female kidneys than those of males. Therefore, the current results indicate that the preferential silver accumulation in female kidneys is not regulated by ovarian hormones, but by elimination rate differences between males and females.