A Single Neonatal Injection of Ethinyl Estradiol Impairs Passive Avoidance Learning and Reduces Expression of Estrogen Receptor α in the Hippocampus and Cortex of Adult Female Rats.

Although perinatal exposure of female rats to estrogenic compounds produces irreversible changes in brain function, it is still unclear how the amount and timing of exposure to those substances affect learning function, or if exposure alters estrogen receptor α (ERα) expression in the hippocampus and cortex. In adult female rats, we investigated the effects of neonatal exposure to a model estrogenic compound, ethinyl estradiol (EE), on passive avoidance learning and ERα expression. Female Wistar-Imamichi rats were subcutaneously injected with oil, 0.02 mg/kg EE, 2 mg/kg EE, or 20 mg/kg 17β-estradiol within 24 h after birth. All females were tested for passive avoidance learning at the age of 6 weeks. Neonatal 0.02 mg/kg EE administration significantly disrupted passive avoidance compared with oil treatment in gonadally intact females. In a second experiment, another set of experimental females, treated as described above, was ovariectomized under pentobarbital anesthesia at 10 weeks of age. At 15-17 weeks of age, half of each group received a subcutaneous injection of 5 μg estradiol benzoate a day before the passive avoidance learning test. Passive avoidance learning behavior was impaired by the 0.02 mg/kg EE dose, but notably only in the estradiol benzoate-injected group. At 17-19 weeks of age, hippocampal and cortical samples were collected from rats with or without the 5 μg estradiol benzoate injection, and western blots used to determine ERα expression. A significant decrease in ERα expression was observed in the hippocampus of the estradiol-injected, neonatal EE-treated females. The results demonstrated that exposure to EE immediately after birth decreased learning ability in adult female rats, and that this may be at least partly mediated by the decreased expression of ERα in the hippocampus

Novel monoclonal antibody recognizing triglyceride-rich oxidized LDLs associated with severe liver disease and small oxidized LDLs in normal subjects

Background: Triglyceride-rich low-density lipoproteins (TG-rich LDLs) in the plasma of patients with severe liver disease are reported to change macrophages into foam cells in vitro. Methods: Male BALB/c mice were immunized with TG-rich LDLs isolated from the plasma of a patient with severe liver disease. The resulting monoclonal antibody (G11-6) was used in a sandwich enzyme-linked immunosorbent assay (ELISA) in combination with polyclonal anti-apolipoprotein B antibodies. The time course of copper-mediated LDL oxidation was monitored using this ELISA. The results were compared to those of the two commercial ELISAs for oxidized LDL using DLH or ML25, thiobarbituric acid reactive substances (TBARS), and the optical absorbance for the conjugated dienes generated in lipid peroxides. Further, the lipoprotein fractions separated by gel filtration were tested with this ELISA in healthy volunteers (n = 11) and patients (n = 3) with liver disease. Results: G11-6 reacted with oxidized LDLs during only the early phase of copper-oxidation, being distinct from the other monoclonal antibodies and methods. G11-6 was confirmed to react with TG-rich LDLs in patients, while it reacted with small LDL particles in normal controls. Conclusions: The monoclonal antibody G11-6 is useful for detecting oxidized small LDLs in normal controls and oxidized TG-rich LDLs in patients with severe liver disease

Neonatal exposure to ethinyl estradiol (EE) decreased the expression level of estrogen receptor alpha (ERα) in the female rat cortex.

<p>A. Representative western blot images showing the ERα expression in the cortex of EE-treated 15–18-week-old ovariectomized (OVX) rats injected with estradiol benzoate (+) or without injection (-). B. The levels of ERα in the cortex. *<i>P</i> < 0.05, Tukey-Kramer test; n = 6/group.</p

Impairment of avoidance learning in ovariectomized (OVX) low dose ethinyl estradiol (LEE)-treated female rats.

<p>The line plots show the effect of LEE (0.02 mg/kg), HEE (2 mg/kg), and 17β-estradiol (E2; 20 mg/kg) treatment within 24 h after birth on the cumulative percentage of rats that displayed a transfer response in the passive avoidance test. All rats were OVX at 10 weeks of age; at 15–17 weeks, the animals were either not injected (A) or injected with EB (B) 1 day before the session. Numerals in parentheses indicate the number of rats in each group. †<i>P</i> < 0.1, log-rank comparison.</p

Neonatal exposure to ethinyl estradiol (EE) decreases the expression level of estrogen receptor alpha (ERα) in the hippocampus of adult female rats.

<p>A. Representative western blot images showing ERα expression in the hippocampus of EE-treated ovariectomized OVX rats injected with (+) estradiol benzoate or without injection (-) EB. B. Levels of ERα expression in the hippocampus. *<i>P</i> < 0.05, Tukey-Kramer test; n = 6/group.</p

Impairment of avoidance learning in gonadally intact low dose ethinyl estradiol (LEE)-treated female rats.

<p>The line plot shows effects of LEE (0.02 mg/kg), HEE (2 mg/kg), and 17β-estradiol (E2; 20 mg/kg) treatment within 24 h after birth on the cumulative percentage of rats that displayed a transfer response in the passive avoidance test. Six-week-old gonadally intact animals were used in this experiment. Numerals in parentheses indicate the number of rats in each group. * <i>P</i> < 0.05, log-rank comparison.</p

Illustration of a coronal section of the brain showing tissue sampling sites for the cortex (a) and hippocampus (b) [25].

<p>CA1: CA1 region of the hippocampus; CA2: CA2 region of the hippocampus.</p