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(Hypertension. 2003;41:1336.)
© 2003 American Heart Association, Inc.

Scientific Contributions

L-Arginine Transport in Humans With Cortisol-Induced Hypertension

Jaye P.F. Chin-Dusting; Belinda A. Ahlers; David M. Kaye; John J. Kelly; Judith A. Whitworth

From the Alfred and Baker Medical Unit, Wynn Domain, Baker Heart Research Institute and Alfred Hospital (J.P.F.C.-D., B.A.A., D.M.K.), Prahran; the Department of Renal Medicine and Medicine, St George Hospital, University of New South Wales (J.J.K.), Kogarah; and the John Curtin School of Medical Research, Australian National University (J.A.W.), Canberra, Australia.

Correspondence to Jaye Chin-Dusting, Baker Heart Research Institute, PO Box 6492, St Kilda Rd Central, Victoria 8008, Australia. E-mail j.chin{at}alfred.org.au

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 [³H]-L-arginine for a period of 5 minutes at 37°C. Forearm [³H]-L-arginine extraction was calculated after infusion of [³H]-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<0.05). Systolic blood pressure was elevated by an average of 7 mm Hg. Neither L-arginine transport into mononuclear cells (placebo vs active, 26.3±3.6 vs 29.0±2.1 pmol/10 000 cells per 5 minutes, respectively, at an L-arginine concentration of 300 µmol/L) nor L-arginine extraction in the forearm (at 80 minutes, placebo vs active, 1 868 904±434 962 vs 2 013 910±770 619 disintegrations per minute) was affected by cortisol treatment; ie, that L-arginine uptake is not affected by short-term cortisol treatment. We conclude that cortisol-induced increases in blood pressure are not associated with abnormalities in the L-arginine transport system.

Key Words: cortisol • hypertension, mineralocorticoid • nitric oxide • arginine • human