Interaction of methotrexate with melanins and melanosomes from B16 melanoma

Abstract

It has been demonstrated that methotrexate forms stable complexes with melanin and melanosomes isolated from B16 melanoma. The number of binding sites and binding constants for methotrexate binding by intact melanosomes and melanin were n = 0.046 μmol/mg, K = 0.32 × 10 4 M −1 and n = 0.063 μmol/mg, K = 1.08 × 10 4 M −1, respectively. Binding of methotrexate to synthetic DOPA-melanin used for comparison also shows a single class of binding sites, n = 0.060 μmol/mg with binding constant K = 2.34 × 10 4 M −1. The possibility of side effects caused by methotrexate-melanin interactions after treatment of neoplasms is discussed.