Effects of quercetin on production and release of endothelin and cGMP from cultured endothelial cells.
AIM
To evaluate the effects of quercetin (Que) on the formation and release of endothelin (ET) and cyclic guanosine monophosphate (cGMP) by endothelial cells.


METHODS
Radioimmunoassay (RIA) was used to assess the amounts of ET and cGMP produced by unstimulated human umbilical vein cells (HUVEC) or HUVEC stimulated with activated platelets and thrombin.


RESULTS
Following the treatment of the cultured HUVEC with activated platelets, the amount of ET in the medium was increased, but no significant effect on cGMP within the cells was seen. Thrombin not only increased the amount of ET in the medium, but also raised the level of cGMP within the cells. Pretreatment of HUVEC with Que 0.5, 5, and 50 mumol.L-1, the release of ET by HUVEC stimulated with thrombin and thrombin-activated platelets was much inhibited. Que 0.5-50 mumol.L-1 markedly increased the amount of cGMP in HUVEC stimulated with thrombin and activated platelets. Que also inhibited the release of ET from unstimulated HUVEC, but increased the production of cGMP from unstimulated EC.


CONCLUSION
Thrombin and activated platelets stimulated the release of ET from HUVEC and Que inhibited the release of ET and promoted the formation of cGMP from HUVEC.