Some Independent and Combined Effects of Copper, Molybdenum, and Zinc on the Placental Transfer of Zinc-65 in the Rat

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Abstract
The effects of increased dietary levels of different combinations of 3 elements: copper (0.01%), molybdenum (0.08%), and zinc (0.50%), were studied in the pregnant rat. Data are presented which suggest that dietary copper and zinc induce a mechanism of competition within the fetus and placental structures (amnion, chorion, yolk sac, allantois, and decidua) resulting in a lower uptake of radiozinc in these tissues. A high level of dietary molybdenum appears to be able to counteract completely the influence of an increased level of dietary copper on this uptake in the absence of increased dietary zinc, and partially overcome the influence of excess copper when it is fed in combination with a high level of zinc. Molybdenum apparently does not elicit a similar action on dietary zinc. Autoradiographic studies conducted on fetuses revealed highest activities, in order of decreasing radiozinc concentration, in: 1) calcifying bones, 2) liver, spleen and lumens of large blood vessels, and 3) kidneys. A highly significant (P < 0.01) increase in zinc-65 urine excretion was observed in rats fed any ration high in zinc and a significant (P < 0.05) increase was noted in animals fed an excess copper and molybdenum diet.