Changes in serum α 2u -globulin levels in male rats given diethylstilbestrol and applicability to a screening test for endocrine-disrupting chemicals

Abstract

alpha2u-Globulin (AUG) is a major rat urinary protein, which has a molecular weight of 16 kDa (kidney type) or 19 kDa (native type). The biosynthesis of this protein is under multi-hormonal regulation. In this study, we investigated changes in serum AUG level and their association with changes in the reproductive organs of male rats after the administration of the estrogenic chemical, diethylstilbestrol (DES) at doses ranging from 0.01 mg/kg per day to 100 mg/kg per day by gavage for 14 days. Our aim was to establish basic data for the development of a new screening method for endocrine disrupting chemicals based on serum AUG levels. DES treatment decreased the weight of testes in a dose-dependent manner; and was accompanied by atrophic histopathological changes in testes. Testis weights were significantly decreased by the group given 1 mg/kg per day DES; however, histopathological abnormalities were found in the group given 0.1 mg/kg per day DES. In four of five animals in the group given 1 mg/kg per day there was no significant decrease in testis weight and only a slight or moderate degeneration of the pachytene spermatocytes. Despite these findings, serum AUG levels in this group decreased markedly, while the serum AUG level markedly decreased even in the animals with no histopathological change in the 1 mg/kg per day or 0.1 mg/kg per day groups with no histopathological change also showed decreased serum AUG level. These results suggest that the serum AUG level may be a sensitive parameter for detecting the activity of estrogenic chemicals in intact male rats. Although a uterotropic assay has been proposed for immature female or ovariectomized female rats and is currently undergoing validation studies internationally, there is no screening method for estrogenic chemicals in intact male animals. More data on AUG changes by treatment with other estrogenic chemicals are needed in order to determine the sensitivity and specificity of this response to estrogens. Nonetheless, an AUG-based screening test for estrogenic chemicals may be useful owing to its applicability to conventional toxicity studies and an apparently higher sensitivity of this parameter compared to organ weight change or histology of testis in intact male rats and applicability to conventional toxicity studies.

Analysis of plasma protein in newborn rats treated with diethylstilbestrol by using rapid micro two-dimensional electrophoresis

“…Genital problems also began to appear in men who had been exposed to DES in utero, such as genital atrophy, non-descended testes that were unable to produce normal sperm, and testicular cancer. These abnormalities have also been confirmed in animal experiments 2) , and DES has also been reported as delaying the production of α 2u -globulin (AUG), which is synthesized in the liver 3,4) .…”

Changes in serum α2u‐globulin levels in castrated male rats treated with testosterone propionate in a Hershberger assay

“…Blood samples were collected from the abdominal aorta at the time of autopsy and the serum was separated by centrifugation. The serum α 2u -globulin levels were determined in all animals using an enzyme-linked immunosorbent assay (ELISA) according to a previously described method (Takeyoshi et al, 2000).…”