Organ Specificity of I131 Labeled Rabbit Kidney Eluates in Rats and Rabbits

Rabbits were immunized against rat kidney. On the assumption that the kidneys of these rabbits would have bound antibodies against kidney tissue, the rabbit kidneys were removed, homogenized, washed, and extracted using mild heat (60°C) or acidity (pH 3.2). The eluted material was labeled with I131, further purified, and injected into rabbits and rats to test for preferential localization. Similar preparations were made using normal rabbit kidneys. Preparations from both sources showed preferential kidney localization in both rats and rabbits persisting for days. Localization was greater for preparations made from immunized kidney, but the difference has not been demonstrated to be statistically significant. One preparation of immunized kidney showed a concentration of I131 in the kidney of injected rabbits fifteen times higher than the next highest organ of thirteen organs studied, the spleen, in rabbits sacrificed three days and a week after injection. Three days following injection of another type of labeled preparation into rabbits, 10% of the injected I131 was found localized in the kidneys. Heat eluted and purified labeled eluates of kidneys from the immunized rabbits, but not normal rabbits, localized in rat small intestine as well as kidney following intravenous injection. It proved possible largely to separate the rat intestine localizing component from the kidney localizing component of these preparations. Preparations made in a similar manner using the heat elution techniques from rabbit spleen, striated muscle, adrenal, and lung showed little kidney localizing tendency when injected into rabbits and rats.