l -Arginine Prevents Corticotropin-Induced Increases in Blood Pressure in the Rat

Abstract

Abstract In this study we examined whether l -arginine treatment could prevent corticotropin (ACTH)–induced increases in blood pressure in the Sprague-Dawley rat. Sixty rats were randomly divided into six groups (n=10): sham injection, ACTH injection (0.5 mg/kg per day in divided doses), l -arginine (0.6%) in food plus sham injection, l -arginine plus ACTH treatment, d -arginine (0.6%) in food plus sham injection, and d -arginine plus ACTH. Systolic pressure, water intake, urine volume, body weight, plasma and urinary electrolytes, and serum corticosterone concentrations were measured. ACTH increased systolic pressure (from 127±2 to 165±6 mm Hg, P <.001), water intake, and urine volume and decreased body weight. l -Arginine reduced ACTH-induced blood pressure rises (130±3 mm Hg, P <.001) but had no effect on blood pressure in sham-treated rats. d -Arginine did not affect blood pressure in sham-treated rats, and systolic pressure in d -arginine+ACTH–treated rats was similar to that of ACTH-treated rats. l -Arginine decreased serum corticosterone concentrations in sham-treated rats (424±43 versus 238±25 ng/mL, P <.01), but d -arginine had no effect. However, both drugs decreased serum corticosterone concentrations in ACTH-treated rats (1071±117 versus 739±95 and 695±72 ng/mL for l - and d -arginine, respectively; both P <.05). As l -arginine but not d -arginine prevented ACTH-induced increases in blood pressure in Sprague-Dawley rats and both l - and d -arginine reduced serum corticosterone concentrations in ACTH-treated rats, the effects of l -arginine in preventing ACTH-induced hypertension were not simply a consequence of decreased corticosterone secretion.