l-Arginine Transport in Humans With Cortisol-Induced Hypertension

A deficient l-arginine–nitric oxide system is implicated in cortisol-induced hypertension. We investigate whether abnormalities in l-arginine uptake contribute to this deficiency. Eight healthy men were recruited. Hydrocortisone acetate (50 mg) was given orally every 6 hours for 24 hours after a 5-day fixed-salt diet (150 mmol/d). Crossover studies were performed 2 weeks apart. Thirty milliliters of blood was obtained for isolation of peripheral blood mononuclear cells after each treatment period. l-Arginine uptake was assessed in mononuclear cells incubated with l-arginine (1 to 300 μmol/L), incorporating 100 nmol/L [ 3 H]-l-arginine for a period of 5 minutes at 37°C. Forearm [ 3 H]-l-arginine extraction was calculated after infusion of [ 3 H]-l-arginine into the brachial artery at a rate of 100 nCi/min for 80 minutes. Deep forearm venous samples were collected for determination of l-arginine extraction. Plasma cortisol concentrations were significantly raised during the active phase (323±43 to 1082±245 mmol/L, P