Determination of urinary 15α-hydroxyestrogen levels via immunoaffinity extraction

Endocrine disrupting chemicals, 4-nonylphenol, bisphenol A and butyl benzyl phthalate, impair metabolism of estradiol in male and female rats as assessed by levels of 15α-hydroxyestrogens and catechol estrogens in urine

Bisphenol A (BPA), 4-nonylphenol (NP) and butyl benzyl phthalate (BBP), termed endocrine-disrupting chemicals, are known to mimic estrogen activity. The effects of these chemicals on 17β-estradiol (E₂ ) metabolism in vivo in rats were examined. Male and female rats were given NP (250 mg kg^-1  day^-1 ), BPA (250 μg kg^-1  day^-1 ) or BBP (500 mg kg^-1  day^-1 ) by gavage for 14 days, followed by a single intraperitoneal injection of E₂ (5 mg kg^-1 ) on the final day. The urinary excretion over 72 hours of 2-hydroxyestrone 1-N-acetylcysteine thioether, 2-hydroxyestrone 4-N-acetylcysteine thioether, 4-hydroxyestrone 2-N-acetylcysteine thioether, 2-hydroxy-17β-estradiol (2-OHE₂ ), 2-hydroxyestrone (2-OHE₁ ), 4-hydroxy-17β-estradiol, 4-hydroxyestrone, 15α-hydroxyestriol (E₄ ), 15α-hydroxy-17β-estradiol and 15α-hydroxyestrone was measured. Increases in urinary excretion of 2-OHE₁ and decreases in E₄ were observed in males treated with NP or BBP. Decreases in urinary excretion of 2-OHE₂ and E₄ were observed in males treated with BPA. Decreases in urinary excretion of 2-OHE₁ and 2-OHE₂ were observed in females treated with BBP. Normalized liver and weights were increased in both sexes treated with NP or BBP. Histologic observations revealed marked changes in the distal tubules and collecting ducts in the kidneys of rats exposed to NP and BBP, and hypertrophy in the hepatocytes of the centrilobular zone of the liver. No BPA-related effects on organ weight and on liver or kidney histopathology were found. These results suggest that the 14 day oral dosing of NP and BBP disrupted E₂ metabolism, resulting from marked morphological and functional alterations in the liver and kidneys. In addition, BPA could induce metabolic and endocrine disruption.