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February 22, 1936


JAMA. 1936;106(8):629-630. doi:10.1001/jama.1936.02770080043015

Pronounced changes occur in the color of the fur of black or "hooded" rats that consume an exclusive milk diet low in copper.1 A progressive decrease in the amount of pigmentation occurred as the dietary regimen continued until finally the coat became a silvery gray. The administration of iron to the animals had no effect on the condition, but the feeding of a small amount of copper promoted a prompt restoration of the normal color to the fur. Almost simultaneously, another investigator2 demonstrated by actual analyses that the copper content of the skin of black rats and rabbits usually exceeded that of otherwise comparable white animals. Further studies suggested that copper might serve as a catalyst in the formation of pigment. Copper, it was shown, markedly accelerated the oxidation of "dopa," 1-3-4-dihydroxyphenylalanine, by "dopa oxidase," an enzyme present in the skin of young animals, forming a dark pigment.