Alteration of endogenous corticosteroids and catecholamines in allergen-induced eosinophilic inflammation in Brown Norway rats

ABSTRACTAlthough various types of stress activate a pituitary adrenal response, the alteration of endogenous corticosteroids and catecholamines during asthma remains unclear. The aim of this study was to assess changes in endogenous corticosteroid and catecholamine levels in allergic eosinophilic inflammation in rats, using metabolic cages. Brown Norway rats (female, 6 weeks old) were sensitized with intraperitoneal injections of ovalbumin on days 0 and 2 and challenged with either an aerosol of ovalbumin or saline for 30 min on day 21. Levels of urinary 11- hydroxycorticosteroid (OHCS), a primary metabolite of corticosterone; epinephrine and norepinephrine were determined in pooled samples taken 0–24 h before and 8–32 h after the challenge. Serum adrenocorticotropic hormone, corticosterone levels and cell counts in bronchoalveolar lavage fluid were assessed 32–36 h after the challenge, as well as lung eosinophil peroxidase activity, an indirect index of eosinophil infiltration. The numbers of total cells and eosinophils in bronchoalveolar lavage fluid and lung eosinophil peroxidase activity were significantly increased in the ovalbumin-challenged rats compared with the saline-challenged rats. While urinary OHCS and serum corticosterone levels were significantly increased after challenge in the ovalbumin-challenged rats, compared with the saline-challenged rats (2.1 ± 0.1 ×10−1 vs 1.7 ± 0.1 x 10−1 mg/g creatinine, P < 0.05 and 482 ± 49 vs 348 ± 19 ng/mL, P < 0.02, respectively), serum adrenocorticotropic hormone levels did not differ between the two groups. Urinary epinephrine and norepinephrine excretion also did not differ between the two groups. It is concluded that endogenous corticosterone, but not catecholamine, increases as a pathophysiologic adrenal response, possibly to protect lung during allergic eosinophilic inflammation