Tyrosinase biosynthesis in adult mammalian retinal pigment epithelial cells

Ulrich Schraermeyer, Jürgen Kopitz, Swaantje Peters, Sigrid Henke-Fahle, Petra Blitgen-Heinecke, Despina Kokkinou, Tobias Schwarz, Karl-Ulrich Bartz-Schmidt


Tyrosinase (EC is the rate limiting enzyme of melanogenesis and it is unclear whether it is synthesized in postnatal retinal pigment epithelium (RPE). Cultured RPE cells from cattle were fed with isolated rod outer segments (ROS). After phagocytosis, RPE cells were tested for tyrosinase presence and activity with three independent methods: (1) ultrastructural DOPA (l-3,4-dihydroxyphenylalanine) histochemistry (2) immunocytochemistry with anti-tyrosinase antibodies (3) measuring tyrosine hydroxylase activity using [(3)H]tyrosine. With all three methods tyrosinase was found in RPE cells after ROS-feeding but was absent without feeding. In contrast to the classical hypothesis, we demonstrated with three independent methods that the expression of tyrosinase and its enzymatic activity are induced in cultured adult RPE by phagocytosis of rod outer segments (ROS) in vitro.

Original languageEnglish
JournalExperimental Eye Research
Issue number2
Pages (from-to)315-21
Number of pages7
Publication statusPublished - 08.2006
Externally publishedYes


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