Alpha-tocopherol but not beta-tocopherol inhibits thrombin-induced PKC activation and endothelin secretion in endothelial cells

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Abstract

Methods and results

In a first set of experiments, cultured bovine aortic endothelial cells (BAEC) were incubated for 48 h with 100 μmol/l α-Toch or vehicle (0.1% ethanol), then cells were stimulated for 4 h or 20 h with thrombin. After stimulating bovine aortic endothelial cells with thrombin for 4 h, α-Toch inhibited PKC activity by 63% and endothelin secretion by 44%, whereas after 20 h of incubation with thrombin, α-Toch decreased the peptide secretion by 51%. In a second set of experiments, BAEC were incubated with increased concentrations (from 0 to 100 μmol/1) of α-Toch or β-Toch, PKC activity and endothelin secretion were measured after thrombin stimulation as previously reported. In these experiments, α-Toch strongly inhibited thrombin-induced PKC activity and endothelin secretion in a dose-dependent manner, whereas β-Toch was more than 10-fold less active than α-Toch in inhibiting these stimulations. Tocopherols (α-Toch + β-Toch) produced a proportional correlation on both PKC stimulation and endothelin secretion by inhibiting the effect of thrombin.

Conclusion

These data suggest that α-Toch strongly inhibits thrombin-induced endothelin secretion in vitro at least partly through PKC inhibition

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