Binding of 85 Sr to Homogenate and Subcellular Fractions of Rabbit Tissues 1

Abstract

Little attention has been given to soft tissue metabolism of strontium nuclides, although extensive studies concerning the deposition of ⁹⁰strontium and other alkaline earth elements in mineralized tissues of mammals have been carried out (1, 2). Kidman, Tutt and Vaughan (3) found less than 1% of the total dose, following parenteral injection of strontium isotopes, in soft tissues of rabbits. More recently, Brues et al. (4) have shown that within a few hours after a single injection of ⁹⁰strontium to male mice, soft tissues may contain higher concentrations of the nuclide than present in the circulating blood. Seminal vesicles (that secrete calcium citrate) and salivary glands (that maintain a high calcium content) contained the highest concentrations of strontium relative to blood. Aberg and Gillner (5) found that iv administration of ⁸⁹SrCl₂ to rams results in spermatozoal uptake of the radionuclide. They also found (6) that 10^-1 atoms ⁸⁹Sr/spermatozoan is sufficient to kill the cells on Day 50 after administration of the isotope. Åberg and Gillner also suggested that the nuclide was most probably bound to spermatozoal DNA although RNA and proteins were not excluded. Wacker and Vallee (7) found strontium tightly bound to isolated RNA preparations from various sources and, to a lesser extent, to DNA preparations.

These data strongly suggest (8) that radiation effects may directly result from fixation of strontium radionuclides to nucleic acid molecules in nucleoprotein-rich tissues in addition to the long-range radiation effects from bone storage of alkaline earth nuclides. The present study, using equilibrium dialysis, provides additional information concerning the in vitro binding of ⁸⁵Sr to homogenates and subcellular organelles of selected rabbit tissues.

Materials and Methods. Frozen adult rabbit tissues were obtained commercially 2 and maintained at —20° until used.