Relation of adrenergic receptors, which have roles in gastroprotective and anti-inflammatory effect of adrenal gland hormones, with cyclooxygenase enzyme levels in rats.

Background And Aims: COX-2 enzyme inhibition is responsible for the anti-inflammatory effects of NSAIDs, COX-1 for their effects upon the gastrointestinal system (GIS), along with other side effects. We investigated the relationship between COX levels and those adrenergic receptors known to play a role in gastroprotection and anti-inflammatory activity.

Method: The effects of adrenaline and prednisolone on gastric COX-1 and COX-2 levels in both intact and adrenalectomized rats treated with doxazosin, yohimbine, propranolol, and metoprolol were determined.

Results: We found that adrenaline increases COX-1 levels in the gastric tissue of both intact and adrenalectomized rats by stimulating alpha-2 receptors. Adrenaline decreases COX-2 levels by stimulating beta-2 adrenergic receptors. Prednisolone inhibits both COX-1 and COX-2 in the gastric tissue of intact rats. In adrenalectomized rats, prednisolone increases gastric COX-1 by stimulating alpha-2 receptors, and decreases COX-2 levels by stimulating beta-2 receptors.

Conclusion: Prednisolone cannot bind to a adrenergic receptors in the presence of adrenaline (intact rats) but, in its absence (adrenalectomy), binds to alpha-2 receptors, and stimulates them more effectively than adrenaline, suggesting a direct relationship between alpha-2 adrenergic receptors and COX-1 levels, whereas beta-2 receptors are directly related to COX-2 levels.