Interaction Between Chemicals and Melanin

Abstract

Various drugs and other chemicals, such as organic amines, metals, polycyclic aromatic hydrocarbons, etc., are bound to melanin and retained in pigmented tissues for long periods. The physiological significance of the binding is not evident, but it has been suggested that the melanin protects the pigmented cells and adjacent tissues by adsorbing potentially harmful substances, which then are slowly released in nontoxic concentrations. Long-term exposure, on the other hand, may build up high levels of noxious chemicals, stored on the melanin, which ultimately may cause degeneration in the melanin-containing cells, and secondary lesions in surrounding tissues. In the eye, e.g., and in the inner ear, the pigmented cells are located close to the receptor cells, and melanin binding may be an important factor in the development of some ocular and inner ear lesions. In the brain, neuromelanin is present in nerve cells in the extrapyramidal system, and the melanin affinity of certain neurotoxic agents may be involved in the development of parkinsonism, and possibly tardive dyskinesia. In recent years, various carcinogenic compounds have been found to accumulate selectively in the pigment cells of experimental animals, and there are many indications of a connection between the melanin affinity of these agents and the induction of malignant melanoma.

Effect of UV irradiation on free radicals in synthetic melanin and melanin biopolymer from Sepia officinalis – EPR examination

“…The linewidths changed after the UVA irradiation of DOPA-melanin-moxifl oxacin complexes [19]. Linewidths of melanin polymers changed after drug binding to melanin [16][17][18][19][20][21] and metal ions [11][12][13][14][15].…”

“…Electron paramagnetic resonance (EPR) investigations confi rmed the existence of free radicals in melanins [1][2][3][4][5][6][7][8][9][10], and melanin complexes with metal ions [1,7,[11][12][13][14][15] and drugs [7,12,[16][17][18][19][20][21]. Dia-and paramagnetic metal ions [11][12][13][14][15] and pharmacological substances [16][17][18][19][20][21] change the intensity of EPR lines of melanin.…”

“…Dia-and paramagnetic metal ions [11][12][13][14][15] and pharmacological substances [16][17][18][19][20][21] change the intensity of EPR lines of melanin. In this study, we concentrate on free radicals in melanins exposed to UV irradiation.…”

Trace elements in scalp hair from potentially exposed individuals in the vicinity of the Bayan Obo mine in Baotou, China

“…As a consequence, hair may reflect tissue metal concentrations. Additionally, melanin pigments can bind cations by ionic interaction at physiological pHs because melanin are polyanionic polymers containing negatively charged carboxyl groups and semiquinones (Larsson, 1993). Moreover, uncharged metals, such as elemental Hg, may also bind to the hydrophobic core of the melanin polymer in the hair structure (Kronstrand et al, 1999).…”

Disposition of 14C-flumequine in eel Anguilla anguilla, turbot Scophthalmus maximus and halibut Hippoglossus hippoglossus after oral and intravenous administration

“…5), can be explained by the ability of flumequine to complex with divalent ions (like Ca 2+ and Mg 2+ ). The affinity of flumequine for skin can be explained by melanin's capacity to bind drugs (Potts 1963, Ullberg et al 1970, Lindquist & Ullberg 1972, Larsson 1993, Fukuda & Sasaki 1994, Howells et al 1994, Salazarbookaman et al 1994. Several studies have reported residues of flumequine and other fluoroquinolones in bone and skin for a long time after the level is below detection in plasma/muscle (Steffenak et al 1991, van der Heijden et al 1993, Elema et al 1994, Martinsen et al 1994.…”