Effect of ageing on levels of zinc in the lymphoid tissues of the rat

To evaluate the effect of ageing on levels of zinc in the spleen and thymus as well as in the serum of rats, we studied three groups of the animals - young adult (3 months old), middle-aged (12-months old), and aged rats (24-months old). Each group contained 10-15 animals. Zinc values were determined by atomic absorption spectrophotometry. Advancing age was associated with a significant increase in spleen zinc (from 21.8 +/- 0.8 to 33.8 +/- 1.0 mu g g(-1) tissue, p < 0.001) and a significant decline in thymus zinc (from 22.7 +/- 1.1 to 15.9 +/- 0.7 mu g g(-1) tissue, p < 0.001). Serum zinc also decreased significantly in the middle-aged rats (from 2.4 +/- 0.2 to 1.7 +/- 0.1 mu g mL(-1), p < 0.01). These findings demonstrate that zinc levels in primary lymphoid tissues are affected by ageing and indicate a possible mechanism by which immune functions progressively decline with age.