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Systemic Ovalbumin Sensitization Downregulates Norepinephrine Uptake by Rabbit Aortic Smooth Muscle Cells

Division of Pulmonary and Critical Care Medicine, and Department of Cell Biology and Anatomy, University of Miami School of Medicine, Miami, Florida; and Department of Respiratory Medicine, Semmelweis University, Budapest, Hungary

Address correspondence to: Adam Wanner, M.D., Division of Pulmonary and Critical Care Medicine, University of Miami School of Medicine, P.O. Box 016960 (R-47), Miami, FL 33101. E-mail: awanner{at}miami.edu

Norepinephrine (NE) concentration at -adrenergic receptors is partially regulated by steroid-sensitive, extraneuronal catecholamine uptake (uptake-2). Because ₁-adrenergic agonist– and glucocorticosteroid (GS)-induced bronchial vasoconstriction is enhanced in individuals with asthma, atopy could be associated with decreased uptake-2 by vascular smooth muscle cells (SMCs). We therefore evaluated whether NE uptake and its specific transporter messenger RNA (mRNA) were reduced in aortic SMCs of rabbits systemically sensitized with ovalbumin (OVA). NE uptake was measured using a semiquantitative fluorescence microscopic method. Corticosterone and O-methyl-isoprenaline, but not desipramine, co-incubation (1 µM each) for 20 min decreased NE uptake into SMCs, an inhibitor profile indicative of extraneuronal monoamine transporter (EMT). In OVA-sensitized rabbits, NE uptake was 25.9 ± 4.5% (mean ± SEM) lower than in control animals (P < 0.05). Sensitized serum had no effect on NE uptake into naive SMCs. EMT mRNA expression was measured in aortic smooth muscle, using multiplex reverse transcriptase-polymerase chain reaction. In OVA-sensitized rabbits, expression was 61.1 ± 16.4% lower than in control animals (P < 0.05). These data demonstrate that NE uptake by aortic SMCs is impaired in atopic rabbits, and associated with a decreased transporter mRNA expression. The same mechanism may operate in bronchial arteries in individuals with asthma.

Abbreviations: complementary DNA, cDNA • catecholamine-O-methyltransferase, COMT • extraneuronal monoamine transporter, EMT • mean fluorescence intensity value, F_N • glyceraldehydes-3-phosphate dehydrogenase, GAPDH • glucocorticosteroid, GS • inhibition constant, K_i • monoamine oxidase, MAO • messenger RNA, mRNA • norepinephrine, NE • neuronal norepinephrine transporter, NET • organic cation transporter, OCT • ovalbumin, OVA • phosphate-buffered saline, PBS • reverse transcriptase–polymerase chain reaction, RT-PCR • smooth muscle cell, SMC • sucrose-potassium phosphate-glyoxylic acid, SPG

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