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Keywords:

  • trans-Resveratrol;
  • platelets;
  • aggregation;
  • calcium;
  • barium;
  • channels;
  • thapsigargin;
  • phytoestrogen;
  • thrombosis;
  • thrombin
  • The phytoestrogenic compound trans-resveratrol (trans-3,5,4′-trihydroxystilbene) is found in appreciable quantities in grape skins and wine. It has been shown that both products rich in trans-resveratrol and pure trans-resveratrol inhibit platelet aggregation both in vivo and in vitro. However the mechanism of this action still remains unknown.

  • An essential component of the aggregation process in platelets is an increase in intracellular free Ca2+ ([Ca2+]i). Ca2+ must enter the cell from the external media through specific and tightly regulated Ca2+ channels in the plasma membrane. The objective of this study was to characterize what effect trans-resveratrol had on the Ca2+ channels in thrombin stimulated platelets.

  • In this study we showed that trans-resveratrol immediately inhibited Ca2+ influx in thrombin-stimulated platelets with an IC50 of 0.5 μM. trans-Resveratrol at 0.1, 1.0 and 10.0 μM produced 20±6, 37±6 and 57±4% inhibition respectively of the effect of thrombin (0.01 u  ml−1) to increase [Ca2+]i.

  • trans-Resveratrol also inhibited spontaneous Ba2+ entry into Fura-2 loaded platelets, with 0.1, 1.0 and 10.0 μMtrans-resveratrol producing 10±5, 30±5 and 50±7% inhibition respectively. This indicated that trans-resveratrol directly inhibited Ca2+ channel activity in the platelets in the absence of agonist stimulation.

  • trans-Resveratrol also inhibited thapsigargin-mediated Ca2+ influx into platelets. This suggests that the store-operated Ca2+ channels are one of the possible targets of trans-resveratrol. These channels rely on the emptying of the internal Ca2+ stores to initiate influx of Ca2+ into the cell.

  • The phytoestrogens genistein, daidzein, apigenin and genistein-glucoside (genistin) produced inhibitory effects against thrombin similar to those seen with trans-resveratrol.

  • We conclude that trans-resveratrol is an inhibitor of store-operated Ca2+ channels in human platelets. This accounts for the ability of trans-resveratrol to inhibit platelet aggregation induced by thrombin.

British Journal of Pharmacology (1999) 128, 149–157; doi:10.1038/sj.bjp.0702749