M. Ahmed et al., EXTRACTION OF NEUROPEPTIDES FROM JOINT TISSUE FOR QUANTITATION BY RADIOIMMUNOASSAY - A STUDY IN THE RAT, Peptides, 15(2), 1994, pp. 317-322
The feasibility of extracting neuropeptides from rat knee joints for q
uantitation by radioimmunoassay was tested. The investigation, based o
n 25 adult Lewis rats, focused on substance P, calcitonin gene-related
peptide, neuropeptide Y, and vasoactive intestinal polypeptide. The r
elative recovery of the peptides in different extraction media was ass
essed. Both knee joints including the articulating epiphysis were diss
ected and cut into small pieces. The series was divided into five subg
roups, 1;0 joints in each, for extraction in five different media: 1)
1 M acetic acid in 4% EDTA, 2) 2 M acetic acid in 4% EDTA, 3) neutral
water in 4% EDTA, 4) 2 M acetic acid in 4% EDTA and 95% alcohol, and 5
) 2 M acetic acid without EDTA. Measureable concentrations of the four
neuropeptides were reproducibly assessed by RIA. Although all extract
ion media provided measurable concentrations, 2 M acetic acid in 4% ED
TA was found to give the highest overall yield of the four neuropeptid
es analyzed. Reverse-phase HPLC confirmed that the immunoreactivities
assessed by RIA corresponded to the four neuropeptides of interest. Ex
perimental and clinical evidence suggest a neurogenic involvement in t
he pathophysiology of inflammatory joint disease, e.g., rheumatoid art
hritis. The extraction procedure described offers a means of determini
ng neuropeptide concentrations in joint tissue under normal and pathol
ogic conditions by RIA.