EFFECT OF AGING ON LEVELS OF SELENIUM IN THE LYMPHOID-TISSUES OF RATS

To evaluate the effects of ageing on the levels of selenium (Se) in th e spleen and the thymus as well as in the serum of rats, three groups of the animals were studied. They represented adult (3 months old), mi ddle-aged (12 months old), and aged rats (24 months old), each group c ontaining 11-15 animals. Se values were determined by atomic absorptio n spectrophotometry. Advancing age was associated with significant dec reases in spleen Se (from 362.9 +/- 34.5 to 103.9 +/- 30.0 ng g(-1) ti ssue p < 0.001) and thymus Se (from 198.5 +/- 18.3 to 111.6 +/- 13.6 n g g(-1) tissue, p < 0.001). Although not statistically significant, se rum Se tended tp decrease with age (from 76.3 +/- 8.4 to 61.7 +/- 4.8 ng mL(-1), p = 0.278). These findings demonstrate that the levels of S e in the primary lymphoid tissues are affected by ageing and may provi de a possible mechanism by which immune functions decline progressivel y with age.