Distribution of copper and zinc in mammalian eyes. Occurrence of metals in melanin fractions from eye tissues

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Abstract
Details of modified standard microprocedures for estimating Cu and Zn are presented. The methods, as applied to eye tissue, are shown to be specific for these metals. Differences in the concns. of Zn and Cu between the various tissues exceed the exptl. error. Ranged in respect of Zn and Cu concns., the tissues fall in roughly the same order in sheep, cattle, whales, and rabbits. The highest concns., in general, are in the pigmented tissues. The Zn content of the iris or choroid of albino rabbit eyes is lower than that of the same tissues of pigmented rabbits. There is no corresponding difference in Zn contentfor the lens or cornea. The''Zn and Cu of irises occur mainly in pigment material found in the supernatant liquor from a trypsin digest of the tissue. The concns. of Zn and Cu are higher in the pigment material than the original tissue, and are not reduced by dialysis. The Zn concn. in the insoluble pigment material is slightly increased by prolonged trypsin digestion, but reduced almost to zero by acid hydrolysis. The Cu concn. is slightly reduced by trypsin digestion and little affected by acid hydrolysis. The ash of dialyzed pigment fractions contains Ca, Mg, Ba, and Fe, in addition to Zn and Cu. Fe appears to be the major constituent.

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