Gastrointestinal peptides in serum and synovial fluid from patients with inflammatory joint disease

The concentrations of immunoreactive vasoactive intestinal polypeptide (ir-VIP), immunoreactive pancreatic polypeptide (ir-PP), ir-somatostatin, and ir-secretin were measured in serum and synovial fluid from patients suffering from various inflammatory joint diseases. One group of patients were not taking any medication, while another group received anti-inflammatory treatment at the time of sampling. High levels of ir-VIP in the synovial fluid were observed in the untreated group of patients, and the concentration of ir-VIP in the synovial fluid was significantly higher than in parallel serum samples. On the other hand, no significant differences in the concentrations of the other peptides were observed either between serum and synovial fluid or between the two groups of patients. It is suggested that VIP is released locally at the inflammatory site and that VIP may be of significance in inflammatory disorders.