Serum Zinc Levels Following Exposure to Ionizing Radiation. ∗

Abstract

An investigation of the trace element zinc in serum as an indicator of exposure to ionizing radiation was predicated upon the role of certain trace elements in important biochemical processes in the living organism. Specifically zinc has been identified in several enzyme systems, i.e., dehydrogenases and pancreatic carboxypeptidase(1,2), and alcohol dehydrogenase and glutamic dehydrogenase (3) in mammalian liver with evidence that zinc is the active enzymatic site and its presence is indispensable to their activity (4,5).

Alteration of enzyme levels in the serum of various mammalian species including man have been reported following exposure to significant amounts of ionizing radiation. In certain of these reports the enzymes were of the zinc containing metalloenzyme groups (6-8). By an investigation of the common denominator of these systems, i.e., zinc, following the radiation insult, it was postulated that a useful pattern of response might evolve allowing application of this parameter as a biologic indicator of exposure to ionizing radiation. Additional support to this concept was given by Wolff(9) who noted increased serum zinc levels in patients undergoing radiation therapy.

Materials and methods. Pure bred Beagle dogs (equal numbers of male and female) in experimental groups of 30 each were utilized. The experimental subjects were individually irradiated using a Cobalt 60 teletherapy unit containing 989 curies of activity while the control group received sham irradiation. The clinical status of the experimental subjects was monitored throughout the post-exposure period. Radiation was delivered at 5.0 R/min, Entrance Air Dose. The target skin distance was 162.5 cm. One half the total dose was delivered to each side of the animal. Constant geometry was maintained by a restraining box constructed of one half inch thickness of lucite (24″×12″×20″). A Siemens-Reinigewerke R-meter was used to calibrate the irradiatior unit and to monitor each exposure.