PRELOADING WITH L-TYROSINE INCREASES THE UPTAKE OF BORONOPHENYLALANINE IN MOUSE MELANOMA-CELLS

To improve the effectiveness of boron neutron capture therapy, the pos sibility of stimulating boron uptake was investigated in an experiment al model. B16F1 mouse melanoma cells were exposed to boronophenylalani ne (BPA). The intracellular boron concentration followed Michaelis-Men ten kinetics in the early incubation phase, In the late phase, cellula r boron concentration was linearly related to the BPA concentration in the culture medium. Incubation with L-tyrosine before exposure to BPA (preloading) increased the intracellular boron concentration by a fac tor of three. It is concluded that in B16F1 cells BPA is transported b y L and presumably ASC (alanine, serine, and cysteine) transport syste ms, and that boron uptake can be effectively stimulated by L-tyrosine preloading.