Distribution of copper and zinc in the eyes of fresh-water fishes and frogs. Occurrence of metals in melanin fractions from eye tissues

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Abstract
Results for the Cu and Zn contents of eye tissues of perch, trout, and frogs are presented. The results of Leiner and Leiner for Zn in perch and trout are confirmed. Most of the Zn, and half the Cu, of the perch choroids is bound in non-ionic form to the pigment-protein fraction of the tissue. The absorption spectra of pigment-protein suspensions from perch and frog eyes differ from those of cattle eyes. On incineration the perch pigment-fraction was found to leave about 10% of the dry weight as ash. Ca, Fe and Sr were constituents of this ash, but almost half is Zn (calculated as metal). The association between Zn and melanin pigmentation is discussed.