Binding of Imipramine, 8-Methoxypsoralen, and Epinephrine to Human Blue and Brown Eye Melanins

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Abstract
Previous studies have shown that although human blue and brown eye melanins are similar in several respects they differ in some physical, chemical, and biological properties. This paper reports a comparison of the binding of three drugs—imipramine, 8-methoxypsoralen, and epinephrine—to the melanins isolated from human blue and brown eyes. It was found that these three drugs are bound to both of these melanins. There were differences between the binding sites and the association constants for their binding to blue and brown eye melanins. The binding of 8-methoxypsoralen to blue eye melanin showed two types of binding sites. It is suggested that the binding of drugs to eye melanins could decrease their immediate concentration in the eyes but could also result in higher concentrations for prolonged periods of time in the eyes compared to concentrations in nonmelanotic tissues. The differences between the blue and brown eye melanins in the binding of certain drugs may result in differences in the activities of the particular drugs in the eye.