Serum and synovial fluid concentrations of endothelin-1 in patients with rheumatoid arthritis

To determine the endothelin-1 (ET-1) concentrations in synovial fluid and s erum of rheumatoid arthritis (RA) patients, this study was designed to exam ine if serum ET-1 concentration of control subjects has any correlation eit her with the ET-1 concentration of synovial fluid or ET-1 concentration of serum from RA patients. Twenty-eight patients were studied of whom eight ma les and twenty females with confirmed rheumatoid arthritis. Twenty-eight he althy volunteers were also included as controls. The immunoreactive concent ration of ET-1 was measured using commercially available radioimmunoassay ( RIA) kits (Peninsula Laboratories, Belmont CA) specific for ET-1. All the s amples were performed in duplicate and after plotting % B/Bo for each stand ard directly on Y axis and endothelin concentrations on the X axis, the "be st fit" curve was drawn and the amount of ET-1 was calculated. Mean ET-1 le vel in synovial fluid was 15.53 +/- 2.82 pg/me. III serum samples from RA p atients, the mean ET-1 level was detected as 16.42 +/- 3.07 pg/ml (n = 28). Sera from twenty-eight healthy volunteers were analyzed as controls and me an ET-1 concentration was 8.68 +/- 1.96 pg/ml. a significant difference (P < 0.001) was found between ET-1 level of sera from RA patients and ET-1 lev els from control sera. Highly significant difference (P < 0.001) was also d etected between synovial fluid ET-1 and control ET-1 levels. However, no si gnificant difference was found between ET-1 levels of synovial fluid and se rum ET-1 levels of RE patients. Results of this study confirmed the presence of elevated levels of ET-1 con centration in synovial fluid and serum samples of patients with RA. The cli nical significance and physiological role of endothelin in synovial fluids and sera of patients suffering from a variety of pathophysiological conditi ons of arthritis deserves further studies.