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N. K. Wills, V. M. Sadagopa Ramanujam, N. M. Kalariya, J. R. Lewis, F. J. G. M. van Kuijk; Distribution of Zinc and Copper in the Human Retina: Effects of Age, Gender, and Cadmium Content. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3437.
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We recently reported that cadmium (a toxic metal with no physiological function that interferes with zinc and copper metabolism) accumulates in human retinal tissues during aging. In this study, we determined the distribution of zinc and copper in the neural retina, retinal pigment epithelium (RPE) and Bruch’s membrane-choroid (BMC) as functions of age and gender. In addition, we evaluated the relationship between these metals and the cadmium content of these tissues.
Two independent methods, graphite furnace atomic absorption spectrometry and inductively-coupled plasma mass spectrometry, were used to measure Cd, Zn, and Cu in human retinal tissues in eyes obtained from donors ranging in age from 1.5 to 87 years. Values were normalized to protein concentration.
Zn levels were ~5 times higher than Cu levels in the same tissues. The relative tissue distributions of these metals were: BMC>RPE>neural retina (Zn) and BMC> RPE=neural retina (Cu). Mean Cu and Zn levels were higher in the BMC from aged donors (≥ 55 yrs old) than young donors (<55 yrs). Levels of these metals were also strongly correlated in the BMC (r2=0.81). Cu and Zn in the neural retina both significantly decreased as a function of age. In the RPE, Cu levels were significantly higher in males than in females. In addition, the cadmium content of the RPE was positively correlated with both Zn and Cu levels in males but not in females.
The results suggest that zinc and copper stores in retinal tissues are co-regulated and might also be affected by cadmium. In addition, gender-related differences exist in copper metabolism in the RPE. Zn and Cu are essential for normal retinal functioning and high-dose supplements of these metals are reportedly beneficial in delaying the progression of advanced stages of age-related macular degeneration. Thus, gender differences in retinal metal transport and the role of cadmium accumulation in aging retinal tissues warrant further investigation.
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