Effect of Zinc Deficiency and Repletion on Thymidine Metabolism

We studied the effect of zinc deficiency on thymidine metabolism in intact and wounded rats. Zinc deficiency was associated with significantly decreased incorpora-tion of [methyl-3H]thymldine into skin DNA of both in-tact and wounded rats, as shown by liquid scintillation counting and autoradlography. With wounding, prolifera-tion-as gauged by the labeling index-increased to about twice normal for zinc-suppiemented rats, but 3.5-fold for zinc-deficient rats. However, despfte the in-creased proliferation rate, wound-healing in deficient rats was always slower than in zinc-supplemented ani-mals. Incorporation of 3H.-iabeled thymidine into spleen DNA at 2 and 4 h, and liver DNA at 4 h was also signifi-cantly less In zinc-deficient rats than in zinc-supple-mented rats. Conversely, DNA synthesis was enhanced In the thymus gland of zinc-deficient rats. Further stud-ies showed that significantly higher percentages of [methyl-’4Cjthymldine were oxidized by zinc-deficient rats. The specific involvement of the methyl group of thymidine was indicated by the observation of normal oxidations of [2-’4Cjthymidine. These findings support the view that zinc directly regulates DNA synthesis. Additional K.yphrases: DNA and RNA metabolism. wound healing #{149}DNA content of rat tissue The essentiality of zinc for animal and human health and optimal growth has been well established. This element had been relatively ignored in the field of biological science until 1934, when Todd and El-vehjem (1) showed the role of zinc in the growth of rats. In 1963, Prasad et al. (2) discovered a new disor-der among children in Iran and Egypt who were af-flicted with anemia and growth and developmental retardation. Furthermore, these conditions were alle-viated by zinc administration (3). Since then, much research and experimentation have been accumulat