Comparison of thymulin activity to other measures in marginally zinc deficient rats (1043.11)

Abstract

Activity of the thymus derived, immunoregulatory peptide thymulin has shown high sensitivity to zinc status in humans. However, this research has generally been done for people with the confounding effects of various health issues. In contrast, a study was done on healthy, semi‐mature growing rats where the only variable was adequate zinc status versus a short term, moderate restriction of zinc intake. After 2 weeks of being fed a diet with 5 ppm zinc, rats showed a mean serum zinc value that was 31% lower than for rats fed 27 ppm zinc. A much bigger mean percent difference of 61% was seen for serum thymulin activity. This activity was determined by a rosette formation assay that uses sheep erythrocytes plus spleen cells from thymectomized mice. Activity was restored to 100% of normal in vitro by adding zinc to the assay. Body weight was lower in the rats fed lower zinc (187 + 5 g vs 242 + 13), but total food intake was not much lower, and was the same per body weight. Serum extracellular superoxide dismutase activity was 18% lower in the low zinc group, and serum 5’‐nucleotidase activity was 26% lower. In addition, liver metallothionein in the low zinc group was about 27% lower than in the zinc adequate group. In conclusion, in rats, a marginal zinc deficiency, with no other confounding factors,produced a larger effect on thymulin activities than on a number of other parameters.