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Decreased density of serotonin 5-HT2A receptors in rheumatoid arthritis
A Kling1, S Rantapää-Dahlqvist, H Stenlund
1Division of Clinical Pharmacology, Umeå University Hospital, S-901 85 Umeå, Sweden. anders.kling@pharm.umu.se
Background:
Animal studies have indicated that 5-HT2A receptors could play a role in arthritic diseases.
Objective:
To analyse the binding properties of 5-HT2A receptors in patients with rheumatoid arthritis.
Methods:
Using a radioactive binding assay, 43 patients with rheumatoid arthritis were compared with 49 sex and age matched controls for density and affinity (measured as Bmax and Kd) of 5-HT2A serotonin receptors. Genotyping, using polymerase chain reaction, was undertaken to exclude the possibility that differences in the genetic polymorphism T102C for the 5-HT2A receptor determine differences in receptor density.
Results:
Mean of Bmax of 5-HT2A receptors in rheumatoid patients was significantly lower than in controls, at 45.3 v 57.4 fmol/mg protein (p = 0.004), but there was no significant difference in Kd. The T102C receptor polymorphism genotypes showed a skewed distribution between the two groups. Even when adjusted for this, there was a significant difference in Bmax between the groups.
Conclusions:
The density of 5-HT2A serotonin receptors in patients with rheumatoid arthritis is markedly reduced. This could either reflect a difference involved in the susceptibility to the disease or be a secondary effect of the disease.
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