title: Roles of accumulated endogenous nitric oxide synthase inhibitors, enhanced arginase activity, and attenuated nitric oxide synthase activity in endothelial cells for pulmonary hypertension in rats.
abstract: Nitric oxide (NO) has been suggested to play a key role in the pathogenesis of pulmonary hypertension (PH). To determine which mechanism exists to affect NO production, we examined the concentration of endogenous nitric oxide synthase (NOS) inhibitors and their catabolizing enzyme dimethylarginine dimethylaminohydrolase (DDAH) activity and protein expression (DDAH1 and DDAH2) in pulmonary artery endothelial cells (PAECs) of rats given monocrotaline (MCT). We also measured NOS and arginase activities and NOS protein expression. Twenty-four days after MCT administration, PH and right ventricle (RV) hypertrophy were established. Endothelium-dependent, but not endothelium-independent, relaxation and cGMP production were significantly impaired in pulmonary artery specimens of MCT group. The constitutive NOS activity and protein expression in PAECs were significantly reduced in MCT group, whereas the arginase, which shares l-arginine as a common substrate with NOS, activity was significantly enhanced in PAECs of MCT group. The contents of monomethylarginine (MMA) and asymmetric dimethylarginine (ADMA), but not symmetric dimethylarginine (SDMA), were increased in PAECs of MCT group. The DDAH activity and DDAH1, but not DDAH2, protein expression were significantly reduced in PAECs of MCT group. These results suggest that the impairment of cGMP production as a marker of NO production is possibly due to the blunted endothelial NOS activity resulting from the downregulation of endothelial NOS protein, accumulation of endogenous NOS inhibitors, and accelerated arginase activity in PAECs of PH rats. The decreased overall DDAH activity accompanied by the downregulation of DDAH1 would bring about the accumulation of endogenous NOS inhibitors.
authors.affiliation: Department of Pediatrics and Developmental Biology, Institute of Biomaterials and Bioengineering, Graduate School, Tokyo Medical and Dental University, Kanda, Tokyo, Japan
authors.forename: Akihito
authors.initials: A
authors.lastname: Sasaki
authors.forename: Shouzaburoh
authors.initials: S
authors.lastname: Doi
authors.forename: Shuki
authors.initials: S
authors.lastname: Mizutani
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Azuma
mesh_terms: D000581:Amidohydrolases / Q000378:metabolism; D000818:Animals; D001119:Arginase / Q000378:metabolism*; D001120:Arginine / Q000031:analogs & derivatives / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D004789:Enzyme Activation / Q000502:physiology; D006976:Hypertension, Pulmonary / Q000139:chemically induced / Q000378:metabolism*; D017380:Hypertrophy, Right Ventricular / Q000139:chemically induced / Q000378:metabolism; D007537:Isometric Contraction / Q000502:physiology; D008168:Lung / Q000098:blood supply; D008297:Male; D016686:Monocrotaline / Q000633:toxicity; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D011651:Pulmonary Artery / Q000166:cytology / Q000201:enzymology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014661:Vasoconstriction / Q000502:physiology
chemical_list: C487735:dimethylarginine; D009569:Nitric Oxide; D016686:Monocrotaline; D001120:Arginine; D052250:Nitric Oxide Synthase Type III; D000581:Amidohydrolases; D001119:Arginase; C059999:dimethylargininase; D006152:Cyclic GMP