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Monitoring differential changes of the mobility of cell membrane components following treatment with a tumor promoter by using pyrene and a novel fatty acid fluorophore.

The effects of an active tumor promoter, 12-O-tetradecanoyl phorbol-13-acetate (TPA), on cell membrane components have been examined using two lipophilic fluorophores, pyrene and 12-[6-(N-methylanilino)-2-naphthalenesulfonyloxy]-stearic acid (MANSOS), in Chang liver cells. MANSOS has a high fluorescence quantum yield in water and shows a blue shift (15nm from the value of 445nm in phosphate buffer) of the emission maximum on incorporation into the cell membrane.Pretreatment of cells with TPA for 2 h induced differential changes in the fluorescence parameters of pyrene and MANSOS incorporated into the cell membrane; it decreased the lifetime and harmonic mean of the rotational relaxation time and amplified the quanching by KI of pyrene fluorescence, whereas it increased the harmonic mean of the rotational relaxation time and slightly attenuated the quenching of MANSOS fluorescence.Taken together, the findings suggest different partition characteristics of the two fluorescent probes in the cell membrane components, and differential effects of TPA on the two species of components as judged from the opposite mobility changes of the two probes.