Adrenocorticotropic hormone, blood pressure, and serum erythropoietin concentrations in the rat

Abstract Background This study was designed to investigate the effects of adrenocorticotropic hormone (ACTH) on systolic blood pressure (BP) and serum erythropoietin (EPO) concentrations in two strains of rats. We hypothesized that ACTH-induced hypertension in the rat is characterized by increased EPO production. Methods Male Sprague-Dawley (SD) and Wistar out-bred (Wistar) rats were treated with saline or ACTH (0.2 mg/kg/d). Systolic BP was measured using the tail-cuff method. Serum EPO concentrations were assayed using an ELISA kit for human EPO, which cross-reacts with but underestimates rat EPO. Thymus weight was used as a marker of glucocorticoid activity. Results In SD rats, ACTH increased systolic BP (from 109 ± 4 to 142 ± 5 mm Hg, P P P P Conclusions 1) ACTH decreased serum EPO concentrations in both strains; 2) EPO is inversely related to ACTH-induced hypertension in the rat; and 3) Wistar rats are relatively resistant to the BP raising effects of ACTH treatment but not to the ACTH-induced decrease in thymus weight. These data suggest that EPO is not causal in ACTH-induced hypertension.