Effects of Acute Dietary Zinc Deficiency in the Rat ∗

Abstract

By means of a diet furnishing about 7 μg of Zn per rat daily, studies at the University of Wisconsin 1-4 have convincingly demonstrated the indispensability of Zn in the nutrition of rats, although the Zn-deficient diet permitted the experimental rats to gain about 8 g per rat weekly during the 10 week period on the diet. 4 The findings have invalidated the conclusion from our laboratory 5 several years ago that the element probably is not a dietary essential. We have recently prepared a diet furnishing not more than 2 to 4 μg of Zn per rat daily. Young rats restricted to it quickly developed extreme degrees of deficiency. Because the studies have been temporarily interrupted, owing to the transfer of one of us (H.G.D.) to another laboratory, we have decided to make a preliminary report on the work at this time.

Diet. The diet was : casein hydrolysate (tryptic)† 15.00, egg white (cooked) 3.00, sucrose 66.29, salts 5.71, butter fat 10.00, and Oleum Percomorphum 50%, 2 drops per 100 g diet (approximately 2800 vitamin A units and 400 vitamin D units).

Each rat was given a daily supplement containing the equivalent of 6.4 g liver, 40 μg of thiamin and 1.0 mg of choline. The liver concentrate,‡ dissolved in 6 volumes of water, was centrifuged. The supernatant solution was transferred to a Pyrex glass separatory funnel and the pH was adjusted to about 6. The solution was extracted repeatedly with dithizone (diphenyl thiocarbazone) dissolved in CC1₄. When no more Zn could be removed Zn-free dilute HC1 was added until the pH was about 4. The excess of dithizone was removed with redistilled CC1₄.