Plasma concentration of asymmetric dimethylarginine, an endogenous inhibitor of nitric oxide synthase, is elevated in hyperthyroid patients.
Cardiovascular manifestations are frequent findings in patients with thyroid hormone disorders. Nitric oxide (NO) plays a key role in vascular, endothelial-mediated relaxation. NO is synthesized from L-arginine by NO synthase, an enzyme inhibited by endogenous compounds, mainly asymmetric dimethylarginine [asymmetric N(G),N(G)-dimethyl-L-arginine (ADMA)]. The aim of our work was to investigate whether plasma L-arginine and dimethylarginine concentrations and NO production are altered in hypo- and hyperthyroid patients, compared with control subjects. L-arginine, ADMA and symmetric dimethylarginine were analyzed by HPLC. NO was measured as plasma nitrite plus nitrate (NO(x)) concentration by a colorimetric method based on Griess reagent. L-arginine, ADMA, and symmetric dimethylarginine plasma levels in the hypothyroid group were similar to those of the control group; whereas in hyperthyroidism, these values were significantly increased. However, the L-arginine/ADMA ratio was decreased in hyperthyroid patients, resulting in diminished NO(x) production. When all subjects were analyzed together, free T(4) levels were directly correlated with ADMA and inversely correlated with NO(x).
Hermenegildo
Carlos
C
Departamentos de Fisiología, Universidad de Valencia and Research Unit (C.H.), Hospital Clínico Universitario de Valencia, E-46010 Valencia, Spain.
Medina
Pascual
P
Peiró
Marta
M
Segarra
Gloria
G
Vila
José M
JM
Ortega
Joaquín
J
Lluch
Salvador
S
D000328:Adult; D000368:Aged; D001120:Arginine / Q000031:analogs & derivatives* / Q000097:blood* / Q000502:physiology*; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood*; D007037:Hypothyroidism / Q000097:blood; D008297:Male; D008875:Middle Aged; D009566:Nitrates / Q000097:blood; D009569:Nitric Oxide / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D009573:Nitrites / Q000097:blood; D009994:Osmolar Concentration; D012016:Reference Values
D009566:Nitrates; D009573:Nitrites; D009569:Nitric Oxide; C018524:N,N-dimethylarginine; D001120:Arginine; D019001:Nitric Oxide Synthase