title: Quantitative cytochemical analysis by microdensitometry of spontaneous or alpha-MSH-stimulated melanogenesis in B16 melanoma cells cultivated in vitro.
abstract: A spontaneous cyclic phenomenon characterized by successive waves of either high proliferative rate or intense melanogenesis is described in non-confluent B16 melanoma cells subcultivated during 2 months (or more). Dopaoxidase activity is quantified in individual cells after L-dopa reaction, by an original method of visible light absorption cytophotometry. A 24-hr treatment with alpha-MSH increases dopa-oxidase activity. This increase is also noted during the following 14 hr, in a fresh medium devoid of alpha-MSH, in which cell proliferation resumes after 24 hr. Phenylthiourea, cycloheximide or actinomycin D inhibit dopaoxidase activity, but also cell proliferation in alpha-MSH pre-stimulated cells. The effects of the two latter agents suggest that de novo synthesis of the enzyme takes place following alpha-MSH treatment.
mesh_terms: D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D003720:Densitometry / Q000379:methods; D008543:Melanins / Q000096:biosynthesis*; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology*; D008545:Melanoma / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D014442:Monophenol Monooxygenase / Q000378:metabolism; D010670:Phenylthiourea / Q000494:pharmacology
chemical_list: D008543:Melanins; D003609:Dactinomycin; D010670:Phenylthiourea; D009074:Melanocyte-Stimulating Hormones; D003513:Cycloheximide; D014442:Monophenol Monooxygenase