Localization of gold in synovial membrane of rheumatoid arthritis treated with sodium aurothiomalate. Studies by electron microscope and electron probe x-ray microanalysis.

The localization of gold in the synovial membrane of rheumatoid arthritis patients treated with sodium aurothiomalate was examined and quantitative analysis of epon-embedded sections was carried out with a wavelength dispersive x-ray microanalyser. Gold was only detected in the lysosomes of synovial lining type A cells and subsynovial mononuclear cells in the form of filamentous deposits and highly electron-dense granules, the latter being few in number. The concentration of gold within the lysosomes containing the characteristic deposits and granules was equivalent to that in epon-embedded standard specimens of freeze-dried albumin in which 2-0-87-4 mg/ml of gold was included. In addition, sulphur was detected in the lysosomes containing the filamentous deposits, but the S/Au x-ray signal ratio was not equal to that detected in sodium aurothiomalate. The significance of the coexistence of gold with sulphur in lysosomes is discussed.