Lymphopenia by Pure Zinc Deficiency : Role of Corticosterone

The effect of zinc deficiency on certain immunological parameters was investigated using intragastric tube feeding to obviate decreased food intake and altered eating pattern. Male, Fischer 344 rats were bilaterally adrenalectomized(ADX) or sham operated(SHAM). ADX rats received 0.9% NaCl in their drinking water and corticosterone injections at the dose of 1mg/kg of body weight three times per day. After recovery, one half of ADX and SHAM animals were tube-fed a purified, liquid diet containing either two ppm of zinc(zinc-deficient, force-fed ; ZDF) or 50ppm(zinc-replete, force-fed ; ZRF) for 19 days. They received identical amounts of diet based on the intake of ad libitum-fed, zinc-replete rats. Although they received identical amounts of food, ZDF rats grew at a slower rate compared to ZRF rats in both SHAM and ADX rats. Regardless of surgery, force-feeding rats the zinc-deficient diet resulted in a substantial decrease in serum zinc levels. The weights of the thymus, lymph node, and spleen were lower in SHAM-ZRF rats compared to SHAM-ARF rats. Marginal zinc deficiency caused lymphopenia in SHAM animals. However, these differences in lymphoid tissues and cells between SHAM-ZDF and SHAM-ZRF rats disappeared in ADX rats. These results indicate that the impaired growth of lymphoid tissues observed in zinc-deficient, sham-operated animals can be attributed to elevated serum corticosterone levels under the conditions of our experiments.