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

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 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. 17β-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.