Interaction between aluminum and zinc or copper and its effects on the pituitary-testicular axis. II. Testicular enzyme and serum gonadotropin assay.

Sprague-Dawley male rats were divided into groups and maintained on a semipurified diet containing either 5 or 40 ppm of zinc or 2 or 8 ppm of copper. Half of the rats in each group received 1000 ppm aluminum in the diet. It was found that aluminum accumulated in the pituitary glands and testes when dietary copper levels were suboptimal. The ALP activity in testes was depressed by the added aluminum when the intake of zinc or copper was suboptimal. SDH, LDH, and LDH-X activities were inhibited and GRS and GGTP activities were elevated in rats fed either the suboptimal zinc or copper diet. However, the added aluminum in the diet reversed the changes to normal levels. The testosterone levels in plasma changed very little when the zinc or copper intake was suboptimal. An increase in plasma FSH was demonstrated in groups of both suboptimal zinc and copper intake. But the plasma LH was elevated only in the group receiving the suboptimal copper diet, and the added aluminum reversed plasma LH to control levels. A lower level of testosterone was demonstrated in the group given suboptimal copper with aluminum. It was concluded that dietary aluminum influenced the pituitary-testicular axis by interacting with certain essential trace metals, particularly zinc.