Membrane estrogen receptor mediates the rapid nongenomic activation of endothelial nitric oxide synthase by estrogen / 生理学报

ABSTRACT

In the present study, confluent bovine aortic endothelial cells (BAECs) were used to study the rapid nongenomic effects of 17beta-estradiol and the membrane impermeable conjugated 17beta-estradiol (E(2)BSA) on the activation of endothelial nitric oxide synthase (eNOS) and mitogen activated protein kinase (MAPK). eNOS activation was assessed in whole cells by measuring [(3)H]L-arginine conversion to [(3)H]L-citrulline. MAPK activity was determined by Western blotting. The results obtained show that the addition of various concentrations of E(2) (0.001-1 micromol/L) resulted in 122+/-29, 186+/-17, 83+/-20 and 157+/-29% increases in eNOS activity, respectively, in BAECs within 15 min of exposure to the hormone. E(2) (0.01 mol/L)-stimulated eNOS activity was detectable during 5-, 15- and 30- min incubation which yielded increases of 37+/-6, 56+/-9 and 38+/-8%, respectively. The increase reached a plateau from 15 through 30 min and rapidly declined thereafter. E(2)BSA 17.5 ng/ml also enhanced eNOS activity by an increase of 35+/-9% above the basal activity. The effect of E(2) and E(2)BSA on eNOS activation was unaffected by actinomycin D 25 microg/ml but was obviously inhibited by tamoxifen (0.1 micromol/L) and PD98059 (50 micromol/L). Compared with control E(2) and E(2)BSA stimulation of BAECs for 15 min caused an increase in MAPK activity by 428+/-17 and 360+/-14% respectively. This effect was blocked by tamoxifen. These results suggest that there might be the membrane estrogen receptor localized on BAECs, which mediates the rapid nongenomic effect of estrogen on eNOS activation through MAPK pathways.