Changes in corticosterone levels under different degrees of acute inflammation in mice.

Carrageenan of different concentrations was injected into the 6-day-old air pouch in mice. It was found that 12 mg carrageenan caused a significant increase of plasma and exudate corticosterone levels at 24 h, while 1 and 3 mg carrageenan could only induce a significant increase of exudate corticosterone at 4 h. Elevation of corticosterone in both plasma and inflammatory exudate appeared to be correlated, suggesting that the exudate corticosterone was derived from the blood circulation. Injection of exogenous histamine and PGE2 into the air pouch induced a significant increase in exudate levels of corticosterone. However, plasma corticosterone increased significantly only after histamine administration, although a slight increase was observed in those injected with PGE2. These findings thus suggest that endogenous histamine and PGE2 which are released during carrageenan-induced acute inflammation, as shown in our previous work, might be responsible for the increase of corticosterone in both plasma and inflammatory exudate.