Metabolism and toxicity of intravenously injected yttrium chloride in rats

Although radioactive yttrium (Y) has been used for medical treatment, little attention has been directed toward the toxicity of Y. We report time-course and dose-related changes in tissue distribution, subcellular localization, clearance, and acute toxicity of iv-injected yttrium chloride (YCl3) in rats. Intravenously injected Y was predominantly distributed to plasma in the blood. At doses more than 0.2 mg Y/rat, most plasma Y appears to be in colloidal material which was composed of proteins and some minerals. Electron microscopic analyses revealed that the colloidal material was taken up by phagocytic cells in the liver and spleen. The liver Y was slowly cleared with a half-time of 144 days at a dose of 1 mg Y/rat. Glutamic-oxaloacetic and glutamic-pyruvate transaminase activities in blood plasma were increased with a peak at 20 hr postinjection at a dose of 1 mg Y/rat and returned to their control values at 170 hr postinjection, indicating that iv-injected YCl3 caused acute hepatic injury. Some of the plasma Ca was translocated to the colloidal material and plasma Ca concentration was increased transiently following injection of YCl3, probably because of resorption of bone. At a dose of 1 mg Y/rat, a significant and tremendous amount of Ca was deposited in the liver (over 10-fold) and spleen (over 100-fold), while Ca concentration was only slightly increased in the lung and kidney (less than 1.5-fold). These results indicate that the liver and spleen are primary target organs of iv-injected YCl3.