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Activation of nitric oxide synthase by β 2 ‐adrenoceptors in human umbilical vein endothelium in vitro
Author(s) -
Ferro Albert,
Queen Lindsay R,
Priest Rachel M,
Xu Biao,
Ritter James M,
Poston Lucilla,
Ward Jeremy P T
Publication year - 1999
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0702512
Subject(s) - isoprenaline , umbilical vein , endocrinology , nitric oxide , medicine , omega n methylarginine , forskolin , nitric oxide synthase , adenylyl cyclase , endothelium , glibenclamide , chemistry , endothelium derived relaxing factor , vasodilation , adenosine , cyclic adenosine monophosphate , stimulation , in vitro , biochemistry , receptor , diabetes mellitus
Some animal studies suggest that β‐adrenoceptor‐mediated vasorelaxation is in part mediated through nitric oxide (NO) release. Furthermore, in humans, we have recently shown that forearm blood flow is increased by infusion of β 2 ‐adrenergic agonists into the brachial artery, and the nitric oxide synthase (NOS) inhibitor N G ‐monomethyl‐ L ‐arginine ( L ‐NMMA) inhibits this response. The purpose of the present study was to determine whether stimulation of human umbilical vein endothelial β‐adrenoceptors causes vasorelaxation and nitric oxide generation, and whether this might be mediated by cyclic adenosine‐3′,5′‐monophosphate (cyclic AMP). Vasorelaxant responses were determined in umbilical vein rings to the nonselective β‐adrenergic agonist isoprenaline and to the cyclic AMP analogue dibutyryl cyclic AMP, following precontraction with prostaglandin F 2α . NOS activity was measured in cultured human umbilical vein endothelial cells (HUVEC) by the conversion of [ 3 H]‐ L ‐arginine to [ 3 H]‐ L ‐citrulline, and adenylyl cyclase activity by the conversion of [α‐ 32 P]‐ATP to [ 32 P]‐cyclic AMP. Isoprenaline relaxed umbilical vein rings, and this vasorelaxation was abolished by β 2 ‐ (but not β 1 ‐) adrenergic blockage, and by endothelium removal or 1 m M L ‐NMMA. In addition, vasorelaxant responses to dibutyryl cyclic AMP were inhibited by 1 m M L ‐NMMA, with a reduction in E max from 90.0±9.3% to 50.5±9.9% ( P <0.05). Isoprenaline 1 μ M increased NOS activity in HUVEC (34.0±5.9% above basal, P <0.001). Furthermore, isoprenaline increased adenylyl cyclase activity in a concentration‐dependent manner; this response was inhibited by β 2 (but not β 1 ‐) adrenergic blockade. Forskolin 1 μ M and dibutyryl cyclic AMP 1 m M each increased NOS activity in HUVEC, to a degree similar to isoprenaline 1 μ M . The increase in L ‐arginine to L ‐citrulline conversion observed with each agent was abolished by co‐incubation with NOS inhibitors. These results indicate that endothelial β 2 ‐adrenergic stimulation and cyclic AMP elevation activate the L ‐arginine/NO system, and give rise to vasorelaxation, in human umbilical vein.British Journal of Pharmacology (1999) 126 , 1872–1880; doi: 10.1038/sj.bjp.0702512