Biochemical studies of the renal radiopharmaceutical compound dimercaptosuccinate

Abstract

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) 2h 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 patttern of ⁹⁹Tc-DMS was in very good agreement with the pattern of ^99mTc-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.