Uraniosomes produced in the synovial membrane by uranyl acetate.

Uranyl acetate was injected into the rabbit knee joint. This produced single-membrane-bound presumably lysosmal bodies (called 'uraniosomes') containing electron-dense crystals in Type A and Type B synovial intimal cells, subsynovial macrophages and lipocytes. Uranium deposits were also seen in the extracellular matrix. All uraniosomes and extracellular deposits analysed by electron-probe X-ray analysis were found to contain uranium, potassium and phosphorus. Traces of calcium and sulphur were also found in some of the uraniosomes and extracellular uranium deposits.