Adrenalectomy and dexamethasone treatment alter the patterns of basal and acute phase response-induced expression of acute phase protein genes in rat liver

Hormonal requirements for full hepatic expression of alpha(2)-macroglobulin (alpha(2)M), alpha(1)-acid glycoprotein (AGP), haptoglobin (Hp) and gamma-fibrinogen (Fb) were assessed at the level of mRNA. Prior to exposure to turpentine-induced inflammation, rats were either depleted of glucocorticoids by adrenalectomy or supplemented with an excess of dexamethasone. Adrenalectomy alone did not affect the basal level of acute phase protein (APP) expression except for alpha(2)M mRNA, the level of which was enhanced. In contrast, dexamethasone treatment alone promoted full induction of alpha(2)M, significant, but not maximal increase of AGP and Hp mRNAs and suppression of Fb. In adrenalectomized rats, acute phase (AP)-cytokines, released in response to inflammation, promoted full expression of Fb and Hp and increased the level of AGP mRNA whereas alpha(2)M mRNA remained at the basal level. Inflammation in dexamethasone pretreated rats elicited changes which, in comparison to mRNA values for dexamethasone unpretreated inflamed rats, were seen as overexpression of alpha(2)M, full expression of AGP and incomplete expression of Hp, whereas Fb mRNA remained at the basal level. These data suggest that glucocorticoids are the principal inducers of a(2)M and AP-cytokines of Fb. For full induction of AGP, additive actions of glucocorticoids and AP-cytokines are required whereas expression of Hp is predominantly controlled by AP-cytokines. (C) 1998 Elsevier Science Ltd. All rights reserved