Question

melanin containing cells are responsible for maintaining the pigmentation in the skin and this is regulated by melanin secreting hormone"

Answer 1

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Answer 2

Answer:

Explanation:

Melanins are a group of natural pigments found in humans and animals. In the eye, melanin is present in the uveal tract and the pigmented epithelial layer of the retina. Melanin is thought to play a protective role through absorbing most of the visible light that penetrates the lens and through binding free radicals [27–29]. In general, basic lipophillic drugs are known to bind melanin. The toxicological consequences of this binding are controversial; it has been proposed that drugs may elicit toxic effects either through accumulation in tissues through melanin binding and prolonged exposure or through binding melanin and interfering with its protective role. Alternatively, melanin–drug complexes may sequester a drug, making it unavailable to elicit toxic effects. Systemically administered drugs that are known to bind to melanin (eg, phenothiazines) and accumulate in the pigmented ocular tissues of animals are also known to elicit ocular toxicity such as retinopathy [30]. It has been proposed that the binding of a drug by melanin involves a “charge transfer” reaction in which the transfer of an electron from the drug to melanin acts as an “electron trap” and thus firmly binds the drug. In the presence of increasing concentrations of chlorpromazine, a drug known to bind melanin, ultraviolet irradiation of bovine retinal epithelial cells inhibits cell growth and elicits cell lysis [31]. However, Leblanc [28] reported that melanin binding was not predictive of drug-induced ocular toxicity, following an extensive review of the literature that included classic examples of drugs both known to bind melanin and being associated with retinal toxicity, specifically, chloroquine and phenothiazines. Furthermore, the authors argued that the albino rabbit, a commonly used nonclinical toxicity model, adequately predicts the absence of toxicity that also occurs in pigmented tissues with the same drug based on review of data in pigmented animals versus albino rabbits.