Biochemical studies of the renal radiopharmaceutical compound dimercaptosuccinate. II. Subcellular localization of 99Tc-DMS complex in the rat kidney in vivo.

In order to extend and confirm our previous studies of in vivo behaviour of 99mTc-DMS in rat kidney cells, the intracellular localization of 99Tc-DMS complex in rat kidney tissue was examined. Animals were injected IV with 99Tc-DMS solution (37 kbq in 1.0 ml) 2 h before killing. Dissected kidneys were homogenized and submitted to differential centrifugation to obtain organelles. The following radioactivity distribution in relation to the total radioactivity of homogenate was obtained in nine experiments: nuclei 3.30% (+/-1.27), mitochondria 9.48% (+/-2.17), microsomes 7.03% (+/-2.34) and cytosol 57.45% (+/-8.01). The subcellular distribution pattern of 99Tc-DMS was in very good agreement with the pattern of 99Tc-DMS binding to kidney cell organelles obtained by the same procedure. Soluble cytoplasmic proteins binding 99Tc-DMS were excluded from a Sephadex G-25 column with the void volume. Their electrophoretic mobility after agarose gel electrophoresis corresponded to beta-lc- and alpha-2-macroglobulins. The results obtained show unambiguously that the investigated complex penetrates into the kidney cells where it binds mostly to soluble cytoplasmic proteins and mitochondria, and to a lesser extent to both microsomes and nuclei. In another series of six experiments, isolated kidney cortical tissue was used, the same procedure was repeated and similar results were obtained.