title: Hydrogen peroxide as a mediator of dopac-induced effects on melanoma cells.
abstract: Dopac increases tyrosinase activity and exerts cytotoxic effects in cultures of human melanoma cells. The possible role of hydrogen peroxide in these actions was examined. Catalase (100 micrograms/ml) completely reversed the cytotoxic action of 0.3 mM dopac and reduced its tyrosinase-stimulating effect by approximately one half. The results show that extracellular hydrogen peroxide is a mediator of both the tyrosinase-stimulating and cytotoxic actions of dopac. Analysis of the degradation products of melanin from dopac-treated melanoma cells after hydriodic acid (HI) hydrolysis revealed the presence of aminohydroxy-phenylacetic acid (AHPAc). This substance is obtained by HI hydrolysis of melanin formed by oxidation of cysteinyl-dopac. Thus, the presence of AHPAc indicates that dopac is transported into the melanocytes where it serves as a substrate for tyrosinase.
authors.affiliation: Department of Dermatology, University of Lund, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Karg
authors.forename: E
authors.initials: E
authors.lastname: Rosengren
authors.forename: H
authors.initials: H
authors.lastname: Rorsman
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000494:pharmacology*; D002374:Catalase / Q000494:pharmacology*; D002460:Cell Line; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000494:pharmacology*; D007980:Levodopa / Q000494:pharmacology; D008543:Melanins / Q000378:metabolism*; D008545:Melanoma; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D010648:Phenylacetates / Q000032:analysis / Q000138:chemical synthesis
chemical_list: D008543:Melanins; D010648:Phenylacetates; D015102:3,4-Dihydroxyphenylacetic Acid; C067219:4-amino-3-hydroxyphenylacetic acid; D007980:Levodopa; D006861:Hydrogen Peroxide; D002374:Catalase; D014442:Monophenol Monooxygenase