Behavior of radiozinc in rat plasma

¹ Laboratory of Nuclear Medicine and Radiation Biology of the Department of Biophysics and Nuclear Medicine, and Department of Radiology, School of Medicine, University of California at Los Angeles, Los Angeles, California

This series of studies was undertaken to determine the behavior of Zn⁶⁵ when injected intravenously as the inorganic ion. A clearance curve for Zn⁶⁵ similar to those of other workers was obtained. It was found that the decrease in clearance and distribution of Zn⁶⁵ was not in direct proportion to the decrease in specific activity. Upon extraction of loosely bound zinc from plasma with dithizone-acetone virtually all of the injected Zn⁶⁵ could be removed up to 1 hr after intravenous injection. However, extraction of the unbound zinc ion demonstrated that more than 90% of the Zn⁶⁵ is bound to protein within the first 3 min after addition of Zn⁶⁵. Dialysis of Zn⁶⁵ against plasma protein showed the Zn⁶⁵ ion is removed by plasma from solution by direct binding to nondialyzable plasma components. Irradiation of rats with supralethal dosages of X ray followed by subsequent injection of Zn⁶⁵ demonstrated that clearance of Zn⁶⁵ from plasma is unaffected by this major alteration of the metabolic state of the animal.