title: Incorporation of [125I]-5-iodo-2-thiouracil in cultured hamster, rabbit, and human melanoma cells.
abstract: The incorporation of [2-14C]-2-thiouracil and a series of [125I]-5-iodo-2-thiouracils ([125I]ISUra(s)) into cultured Greene hamster melanoma cells was determined in order to establish their properties as false precursors in the melanin-biosynthetic pathway. The cold trichloroacetic acid-precipitable incorporation of [2-14C]-2-thiouracil as well as [125I]ISUra into melanoma cells after a 24- to 48-hr labeling period proved to be completely tyrosinase dependent (more than 99.5% inhibition could be achieved by 0.5 mM phenylthiourea). [125I]ISUra incorporation was 3-fold higher than was [2-14C]-2-thiouracil incorporation and was enhanced by 1 mM theophylline treatment. [125I]ISUra incorporation into hamster, rabbit, and human melanoma cells showed a linear relationship with cell melanin content. Methylation of the sulfur completely prevented the incorporation, while propylation but not methylation at position 6 resulted in lower incorporation. [125I]ISUra proved to be a marker for melanogenesis and may be useful in studies on the differentiation of cultured melanoma cells.
mesh_terms: D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D006224:Cricetinae; D006801:Humans; D008543:Melanins / Q000096:biosynthesis; D008545:Melanoma / Q000378:metabolism*; D010670:Phenylthiourea / Q000494:pharmacology; D011817:Rabbits; D013889:Thiouracil / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D008543:Melanins; D013889:Thiouracil; C036667:iodothiouracil; D010670:Phenylthiourea