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.

Effect of carrageenan-induced acute inflammation on corticosterone levels in mice.

Changes in corticosterone levels in plasma and inflammatory exudate were studied in the 6-day-old air pouch of mice. The pouch inflammation in the test group was induced by the injection of carrageenan prepared in physiological saline while the control received only the physiological saline. The results show that exudate and plasma of both groups showed a rapid rise in corticosterone as measured after 30 min and this early rise was probably due to the resulting effect of the ether used during the injection of irritant or vehicle. In contrast, corticosterone levels in the inflammatory exudate of the test group increased with time, reaching a peak at 24 hours after the carrageenan injection. The increased corticosterone levels in the inflammatory exudate appeared to be closely correlated with the increased exudate cell accumulation. This suggests that the increased accumulation of exudate corticosterone in the pouch might play an important role at the inflammatory site by modulating intensity of the inflammatory reactivity caused by the irritant.