The effect of long-term exposure to combinations of growth promoters in Long Evans rats: part 2. Adrenal morphology (histopathology and immunochemical studies)

The aim of the study was to investigate the effects of long-term exposure (45 days) to growth promoters: clenbuterol (CB: 1 mg kg(-1) bw) and/or dexamethasone (DEX: 0.1 mg kg(-1) bw), in adrenal gland morphology, and the possibility of recovery after the withdrawal of drug treatment. Animals were sacrificed at different days of withdrawal (W0, W5, W10, W15 and W20), and adrenal glands processed for histopathology and immunohistochemistry. Adrenals of CB treatment showed typical features of long-term administration of beta-agonists at W0 such as capillary dilatation in the fasciculata-reticularis zone, and this feature was also presented at W20. Adrenals of CB+DEX treatments showed the same results of CB treatment at days W0 and W20. However, DEX treatment presented the typical results of the exposure to corticoids with the atrophy of adrenal cortex. Immunohistochemistry of adrenal cortex steroidogenic enzymes (P450: scc, 3beta-HSD, aromatase) denoted that neither positive staining nor localization was affected by treatments. Aromatase enzyme was immunolocalized in adrenal medulla cells in controls as well as in treated groups. The immunolocalization of glucocorticoid receptors showed an increase in CB (+++) and CB+DEX (++) treatments compared to the control group (0) and DEX treatment (0). Histopathological and immunohistochemical results are closely related to those found for adrenal endocrine function. We can conclude that chronic administration of growth promoters influence adrenal morphology and glucocorticoid receptor expression.