Effects of melanin on high- and low-linear energy transfer (LET) radiation response of human epithelial cells

The search for effective radioprotectors is of major concern in the medical, military, environmental, and space sciences. Conventional radioprotectors are generally effective only during a single irradiation and display their radioprotective properties only at high, toxic concentrations. In addition, they reduce somatic radiation effects but are poorly efficient in protecting from hereditary stochastic radiation effects. In this respect, the pigment melanin merits attention. Experiments referring to potential melanin effects on the ionising radiation response have been carried out with different biological systems, both in vivo and in vitro. In this paper, we present results on the response to high-and low-linear energy transfer (LET) radiation of a human mammary epithelial cell line, H184B5 F5-1 M/10, supplemented by melanin. The incorporation of auto-oxidative (L-dopa) melanin was linear for concentrations from 3 to 10 mu g/ml in the growth medium. Concentrations of up to 250 mu g/ml did not significantly impair the cells proliferative ability. No significant protective effect of melanin on the survival of cultured cells after exposure to alpha-particles (130 keV/mu m) or x-rays was observed.