title: MSH binding in Bomirski amelanotic hamster melanoma cells is stimulated by L-tyrosine.
abstract: Bomirski Ab amelanotic melanoma cells have recently been shown to undergo striking phenotypic changes when precursors of the melanogenic pathway, L-tyrosine and L-dopa, are added to the culture medium. The changes include increased tyrosinase activity and de novo synthesis of melanosomes and melanin. L-tyrosine and L-dopa appeared to elicit these responses through separate but overlapping regulatory pathways. Here we show an additional effect of L-tyrosine: stimulation of MSH binding capacity. Cells cultured for 24-48 hours in the presence of 200 microM L-tyrosine display a 3-4 fold increase in their ability to bind 125I-beta-MSH. L-dopa did not stimulate MSH binding under the same conditions. In control experiments neither L-tyrosine nor L-dopa had any effect on insulin binding. The amelanotic cells respond to MSH with increased dendrite formation, increased tyrosinase activity without melanin production, and decreased growth rate.
mesh_terms: D000818:Animals; D006224:Cricetinae; D007328:Insulin / Q000378:metabolism; D007980:Levodopa / Q000494:pharmacology; D009074:Melanocyte-Stimulating Hormones / Q000378:metabolism*; D008546:Melanoma, Experimental / Q000378:metabolism*; D014442:Monophenol Monooxygenase / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D014443:Tyrosine / Q000494:pharmacology*
chemical_list: D007328:Insulin; D014443:Tyrosine; D007980:Levodopa; D009074:Melanocyte-Stimulating Hormones; D014442:Monophenol Monooxygenase