for rats: effects of chronic exposure to corticosterone in drinking water on corticosterone kinetics, blood chemistry, and concentrations of catecholamines in parts of brain were studied in Long-Evans rats. Rats were randomly grouped into 3 x 2 treatments (n=4), with three treatments of drinking water (tap water, or 2.5% ethanol, or 400 microg/mL of corticosterone in 2.5% ethanol) for 28 days and two treatments of gavage with a single dose of either corn oil or corticosterone 20 mg/kg on day 28. Blood samples were collected at 0, 15, 30, 60, 120, 240, 480, and 720 min after dosing to determine plasma corticosterone concentrations.

Fibroblast-like synovial cells of rat were stimulated with 10 ng/ml interleukin (IL)-1β for 24 h, and were subsequently, within the next 24 h, treated with or without 10-6 mmol/l corticosterone alone or with 100 nmol/l PF915275. At the end of the second 24 h, PGE2 levels in culture supernatants were assayed. Corticosterone was demonstrated to suppress the mRNA expression levels of inflammatory factors, such as TNF-α and PGE2, induced by IL-1β in vitro. Simultaneously, expression levels of 11β-HSD1 decreased significantly at the mRNA and protein levels (P<0.05).