Zinc and Glucocorticoids

The release of glucocorticoid hormones from the adrenal glands can cause thymic atrophy. Since Zn deficiency raises blood glucocorticoid levels, thymic atrophy may be mediated, in part, by glucocorticoids (DeRasquale-Jardieu and FTaker, 1980; Concordet and Ferry, 1993). Indeed, when adrenalectomized mice were maintained up to 6 weeks on a Zn-deficient diet, changes in thymic weight were small or absent (DeRasquale-Jardieu and Fraker, 1980). In addition, when adult mice were given a slow-release corticosteroid implant, thymus size was reduced more than 80%. Steroid-implanted mice also showed large reductions in pre-B and immature B-cells in the bone marrow, suggesting that the effects of Zn deficiency on early B-cell development may also involve glucocorticoids. The contribution of glucocorti-coids to the effects of Zn deficiency must, however, be interpreted with caution. Zn deficiency has profound effects on human thymocytes, which are relatively resistant to glucocorticoids (DeRasquale-Jardieu and Fraker, 1980). In addition, although the thymus of Zn-deficient adrenalectomized mice remained normal in size, Zn-depen-dent decreases in the ratio of the areas of the cortex to the medulla still occurred. Likewise, in adrenalectomized mice, Zn deficiency reduced IgM and IgG responses to sheep red blood cells, with 50% of the loss in T-cell helper function occurring before detectable increases in plasma corticosterone. Lastly, in marginally Zn-deficient mice, loss of lymphocytes in the spleen, depressed immunity and decreased IL-2 production were observed despite the absence of thymic shrinkage or increased glucocorticoid levels.

0 0

Post a comment