Excitatory amino acid profiles of synovial fluid from patients with arthritis.
OBJECTIVE
Previous studies in an experimental synovitis model in rats determined that administration of glutamate and aspartate into the joint produces hyperalgesic responses, while their receptor antagonists provide protection against the development of a hyperalgesic state. We examined concentrations of amino acids in synovial fluid (SF) to determine if increases might be relevant to human joint pathology.


METHODS
One hundred forty-four repository SF samples from patients undergoing diagnostic or therapeutic arthrocentesis and 14 SF samples from 7 cadavers were analyzed by high pressure liquid chromatography and compared as arthritic and control cohorts.


RESULTS
Compared to the average concentrations from the autopsy cases, the excitatory amino acids (EAA) glutamate and aspartate in SF from patients with synovitis were 54 and 28 times higher, respectively. Increases for all other amino acids ranged from 3 to 18-fold. The values for glutamate and aspartate were significantly higher than the mean increase for other amino acids compared using unpaired t tests (p < 0.0001). The mean ratio of glutamate and aspartate elevations over the mean increase for other amino acids was 4-fold and 2-fold, respectively. The EAA were highest in Reiter's, infectious arthropathies, and systemic lupus erythematosus, but did not appreciably segregate to diagnosis or SF white blood cell count.


CONCLUSIONS
Our data provide evidence of increased glutamate and aspartate in the SF of humans with active arthritis, suggesting that glutamate mediated events may contribute to the pathogenesis of human arthritic conditions.
McNearney
T
T
Department of Internal Medicine, University of Texas Medical Branch, Galveston 77555-0759, USA.
Speegle
D
D
Lawand
N
N
Lisse
J
J
Westlund
K N
KN
D000293:Adolescent; D000328:Adult; D000368:Aged; D001168:Arthritis / Q000378:metabolism*; D016918:Arthritis, Reactive / Q000378:metabolism; D001224:Aspartic Acid / Q000032:analysis; D002648:Child; D002675:Child, Preschool; D002851:Chromatography, High Pressure Liquid; D015331:Cohort Studies; D018846:Excitatory Amino Acids / Q000032:analysis*; D018698:Glutamic Acid / Q000032:analysis; D006801:Humans; D007592:Joint Diseases / Q000378:metabolism; D008180:Lupus Erythematosus, Systemic / Q000378:metabolism; D008875:Middle Aged; D012016:Reference Values; D013582:Synovial Fluid / Q000737:chemistry*; D013585:Synovitis / Q000378:metabolism
D018846:Excitatory Amino Acids; D001224:Aspartic Acid; D018698:Glutamic Acid