Effects of dietary protein concentration on trace minerals in rat tissues at different ages

Copper, iron and zinc concentrations were measured in tissues of young (2 mo), mature (14 mo) and aged (26 mo) male Fischer rats fed either a normal protein (16% casein) or high protein (32% casein) diet for 30 d. Spleen copper concentrations decreased with maturity but were not affected by dietary protein level. Age, dietary protein and age X protein interaction affected spleen iron concentrations. Splenic iron was increased significantly only in mature and aged rats fed the normal protein diet. High protein-fed aged rats had decreased splenic zinc. High protein feeding increased renal zinc in the young and aged rats compared to normal protein feeding. At both protein levels, liver iron increased in the mature rats. Upon aging, zinc levels in the heart increased in the normal protein group and decreased in the high protein group. A significant interaction between age and protein was observed on heart zinc. Thus, the concentrations of tissue trace minerals are affected by age, dietary protein and protein X age interaction in young, mature and aged male rats.