The extracutaneous pigmentary system: evidence for the melanosynthesis in Amphibia and Reptilia liver

1) In vitro incorporation of (14C) L-tyrosine and (14C) L-DOPA into purified melanin extracted from frog and turtle liver after incubation of surviving tissue and purified melanosomes were measured. 2)The results show an incorporation of labelled precursors in melanin both in incubating tissue slices and incubating isolated melanosomes and that the radioactivity detected in purified melanin was not due to an adsorption or binding phenomenon of labelled tyrosine. 3) We conclude that melanins occuring in the pigment cells of Amphibia and Reptilia liver originate from the melanosynthetic activity of Kupffer cells and that these pigment cells are to be considered as belonging to the extracutaneous pigmentary system.