Effect of long-term exposure to combinations of growth promoters in Long Evans rats Part 1.: Endocrine ovarian function

The aim of the study was to investigate the effects of long-term exposure (45 days) to growth promoters: clenbuterol (CB; I mg kg(-1) body weight) and/or dexamethasone (DEX; 0.1 mg kg(-1)), in rat endocrine ovarian function and the possibility of recovery after the withdrawal of drug treatment. Animals were sacrificed at different days of withdrawal (W0-W20). Hormone profiles were as follows. Progesterone: CB-treated rats showed significantly lowered plasma (P < 0.01) and elevated ovarian levels until 10 days of withdrawal (P < 0.01); (CB + DEX)-treated rats showed both increased plasma and ovarian levels (P < 0.001); DEX-treated rats showed elevated plasma and lowered ovarian levels during the whole withdrawal. 17beta-Estradiol: CB-treated rats showed significantly elevated plasma until 10 days of withdrawal and lowered ovarian levels during the whole withdrawal (P < 0.001); (CB + DEX)-treated rats showed significantly elevated plasma and lowered ovarian levels during the whole withdrawal (P < 0.001); DEX-treated rats showed increased plasma and ovarian levels (P < 0.001). It was concluded that long-term administration of clenbuterol and/or dexamethasone causes an endocrine ovarian disruption with changes in ovarian steroid secretion. However, after a 20-day withdrawal period, ovarian endocrine function was recovered in CB-treated rats. (C) 2002 Elsevier Science B.V. All rights reserved.