Modulation of melanogenesis and antioxidant defense system in melanocytes by amikacin. 
Amikacin is principally used to treat infections caused by microorganisms resistant to other aminoglycosides.  Ototoxicity is one of the side effects of amikacin, but the causative mechanism of damage to the ear has not been fully established.  Thus, the aim of this work was to examine the impact of amikacin on the melanogenesis and antioxidant defense system in cultured human normal melanocytes (HEMa-LP).  Amikacin induced the concentration - dependent loss in melanocytes viability.  The value of EC50 was determined to be ~7.5 mM. The analyzed antibiotic inhibited melanin biosynthesis in concentration-dependent manner.  Increasing the amikacin concentration also resulted in a decrease in cellular tyrosinase activity.  To study the antioxidant defense system in melanocytes, the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) in cells exposed to amikacin were determined.  Significant changes in cellular antioxidant enzymes activities were observed.  Modulation of melanogenesis and the antioxidant status of melanocytes resulting from the use of amikacin in vitro may explain a potential role of melanin and melanocytes in the mechanisms of aminoglycosides ototoxic effects in vivo.