Comparative effects of iron deficiency induced by bleeding and a low-iron diet on the intestinal absorptive interactions of iron, cobalt, manganese, zinc, lead and cadmium.

Dietary iron deficiency enhances the absorption of iron, cobalt, manganese, zinc, cadmium and lead, whereas, iron deficiency due to bleeding increases the absorption of iron, cobalt and perhaps manganese. To determine whether the response to bleeding is qualitatively different from that induced by dietary iron deficiency, metal absorption was studied in mice fed either a high-iron diet (120 ppm Fe) and bled (0.5 ml) or fed a low-iron diet (< 3 ppm Fe). Iron absorption from an intragastric dose was increased by the loss of 0.5 ml of blood; smaller losses of blood had no effect. Also, iron absorption was increased more by dietary iron deficiency than by bleeding. In perfusion experiments, bleeding increased the duodenal absorption of only iron and cobalt, whereas dietary iron deficiency enhanced the absorption of all the metals except cadmium. The patterns of absorptive inhibition of the metals by each other were similar in bled mice and in mice with dietary iron deficiency except that interactions among metals with lower affinities for the iron absorption mechanism--manganese, zinc, cadmium and lead--were more obvious in mice fed the low-iron diet. We concluded that bleeding only partially activates the iron absorptive mechanism and that the lack of a bleeding effect on the absorption of manganese, zinc, cadmium and lead results from the weaker interactions of these metals, with a partly-activated absorption process.