Effect of dietary iron deficiency on the pigmentation and iron content of rat incisor enamel

abstract — The enamel of rat incisors is characterized by a pigmented, iron-rich surface layer. The Fe content and degree of mineralization of this enamel layer in rats fed an Fe-deficient diet were studied using the electron microprobe. Four groups of eight 24-day-old rats were fed a milk diet, Fe-fortified milk diet, Cu-fortified milk diet, and Fe+Cu-fortified milk diet, respectively, for 10 weeks. At the end of the experimental period, incisor pigmentation was markedly reduced in the animals fed the Fe-deficient diets. Close to the enamel surface, the Fe content averaged 1.9% in the midsagittal area, as opposed to 9.9% Fe in the controls. Variation of Cu supply had no effect on hemoglobin values or Fe content of incisor enamel. In a second experiment, rats were fed a milk diet with and without Fe supplementation. Nearly colorless incisors from animals sacrificed after 16 weeks on the milk diet contained 1.9% Fe (range 1.4–2.5%) close to the enamel surface. In this region, the Ca content averaged 33.7% and P 17.2%. Normally orange-colored incisors from animals receiving the Fe-supplemented diet contained, in the same region, 9.9% Fe (9.3–10.5%), 28.9% Ca, and 16.0% P. While pigmentation and Fe content of incisor surface enamel were markedly reduced as a result of the Fe-deficient diet, the Ca and P contents had increased to values similar to those found in non-pigmented subsurface enamel. The Ca/P weight ratio of incisor surface enamel was 1.96 in the iron-deficient animals and 1.81 in the controls.