The effect of clenbuterol on adrenal function in rats

The use of anabolic agents is illegal in the European Community but the eff ect of these agents on animal welfare is not well documented. The aim of th is study was to evaluate whether the administration of anabolic agents, suc h as clenbuterol, causes stressful effects in rats, as reflected by the adr enal function. Anabolic doses of clenbuterol (1 mg kg(-1), 99% purity) were administered orally by stomach tube daily for 45 d to female Long Evans ra ts (250-300 g, n = 50). Twenty-five animals were used as controls. Blood sa mples were collected from the jugular vein in anaesthetised animals (ketami ne and xylazine). At the end of the experiment, the animals were sacrificed and the adrenal glands were removed. Hormonal levels were measured by an e nzyme immunoassay previously validated for this species. Hormonal levels of cortisol and corticosterone, and histopathological analysis, were used as indicators of the adrenal function. Increased corticosterone and cortisol s ecretion was found in the treated group (p < 0.001), both in adrenal homoge nates and peripheral blood samples, compared with control animals. Higher r elative adrenal gland weight (adrenal gland-to-body weight ratio) was also found in the treated group (p < 0.01). The major histopathological finding was the presence of hyperplasia in the adrenocortical cells. It was conclud ed that the administration of an anabolic dose of clenbuterol causes a hype rstimulation of adrenal gland secretion that could adversely affect animal welfare.