Pheomelanin from human red hair (RHM) produces considerably more cellular damage in Ehrlich
ascites carcinoma cells when subjected to radiations of wavelength 320-700 nm than
eumelanin from black hair (BHM). Irradiation of RHM generated large amounts of
superoxide while BHM did not produce detectable amounts of
superoxide. The present investigations describe the effects of irradiation of mast cells in the presence of various natural and synthetic
melanins. Irradiation of mast cells in the presence of RHM and red hair melanoprotein released large amounts of
histamine while BHM and synthetic
melanins prepared from
dopa,
cysteinyldopa, or a mixture of
dopa and
cysteinyldopa did not release
histamine. The release of
histamine at lower concentrations of RHM was not accompanied by the release of 51Cr from
chromium-loaded cells, suggesting that this release was of noncytotoxic nature. On the other hand, the release of
histamine at higher concentrations of RHM was due to cell lysis since both
histamine and cytoplasmic marker 51Cr were released to the same extent. The release evoked by large concentration RHM was not inhibited by
superoxide dismutase or
catalase. This suggests that the cell lysis under these conditions was not due to H2O2 or O-2. The finding that mast cells release
histamine when irradiated in the presence of RHM suggests that the immediate and late-phase reactions seen in
sunburn may in part be due to the release of mediators from these cells.