1. In a series of thirteen patients with rheumatoid arthritis and eleven control subjects clearance rates of 133Xe and 99mTc from the knee joint were monitored before and after oral administration of the anion-transport inhibitor potassium perchlorate.
2. The clearance rate of 99mTc was reduced following perchlorate administration although there was no change in the 133Xe clearance rate. This suggests the presence of a perchlorate-blockable anion-transport mechanism across the synoviocyte.