MANAGEMENT OF DIETARY ESSENTIAL METALS (IRON, COPPER, ZINC, CHROMIUM AND MANGANESE) BY WISTAR AND ZUCKER OBESE RATS FED A SELF-SELECTED HIGH-ENERGY DIET

The balances and content of essential elements (iron, copper, zinc, ch romium and manganese) in the body of Wistar, Zucker lean and Zucker ob ese rats fed a reference or cafeteria diet from day 30 to 60 after bir th have been studied. Intestinal iron absorption compensated for low i ron content of the cafeteria diet and the extra needs of growth and fa t deposition. It can be assumed that the altered energy regulation pro cesses that afflict the genetically obese rat are not directly related to altered iron metabolism. Obese Zucker rats had lower copper tissue concentrations than lean rats, but when fed a cafeteria diet the diff erences between Zucker rats strains disappear. This cannot be traced t o large differences in diet copper concentration. A low diet availabil ity of zinc-such as that of cafeteria-fed fa/fa rats-is easily compens ated for by increasing absorption. So, as a consequence, we can conclu de that genetic obesity did not impair zinc absorption. There was no d eficit of zinc in any of the groups studied; the rats have enough capa city to extract zinc within a wide range of dietary concentrations. Th e absorption of dietary chromium was inversely proportional to its con centration. The ability to extract chromium from the diet and the very low urinary losses are a consequence of its scarcity in most dietary items. Despite wide variations in the manganese of the diets, the abso rption rates were practically unchanged except for obese rats fed the cafeteria diet. It seems that this low absorptive capacity is enough t o supply the rat with the manganese it needs, since a sizeable-but sub jected to 8-fold-span variations-proportion is lost in the urine. This alone points towards a considerable excess of manganese in both diets studied. Obesity does not have a significant effect on the abilities to absorb and retain minerals, since these processes were more related to dietary availability. Management of essential metals by obese rats depends whether this condition is genetic or induced by diet. Most of the differences observed can be related to differences in diet concen tration, to the excess fat content or different metabolic attitude to use substrates of obese animals. The data presented show that the cafe teria diet used adequately serves the mineral needs of the rat, since the rat adapts its absorbing and retaining strategies to match the die tary availability of these minerals.