Uptake of 90Y Resin Colloid by Synovial Fluid Cells and Synovial Membrane in Rheumatoid Arthritis: A Radioautographic and Electron Microscopic Study

The distribution of 90Y resin colloid in the synovial fluid is a simple dispersion between two colloidal systems. 90Y particles are rapidly phagocytized by synovial fluid cells, as shown by radioautography. In synovial biopsies taken for electron microscopic study 3 or 6 days after therapeutic isotope injection, the 90Y particles were abundant in vacuolar cavities among the intercellular ground substance. This is considered to be the route by which 90Y leaks into the lymph stream. The acute effect of the isotope was due to damage of the synovial cells and superficial synovium.