Immunoreactive tachykinins, calcitonin gene-related peptide and neuropeptide Y in human synovial fluid from inflamed knee joints.

We have analysed the concentrations of substance P (SP), neurokinin A (NKA), calcitonin gene-related peptide (CGRP) and neuropeptide Y (NPY) in the synovial fluid from 5 patients suffering from arthritis with inflamed knee joints as well as from 5 healthy control subjects with an earlier traumatic meniscal or cruciate ligament injury. Competitive radioimmunoassay was done using antisera SP2 (SP), K12 (NKA), R8 (CGRP), and NPY1 (NPY). No SP-like immunoreactivity (-LI) was detected in any patient. NKA-LI was found in all control patients but in none of the arthritis patients. CGRP-LI was seen in all arthritis patients as well as in 3/5 control patients, a non-significant difference. NPY-LI was found in a significantly higher concentration in the arthritis group vs the control patients. The results support an involvement of neuropeptides in human joint inflammation.