Modulation of platelet activity by E2-treated HUVECs, E2, or AEA.

(A) Effect of 10-minute coincubation with HUVECs (1 × 10⁶ cells/test) on the release of [³H]5-HT from human platelets (5 × 10⁹cells/test). Endothelial cells were pretreated with 100 nM E2, alone or in the presence of 100 nM TMX or of 100 U/mL FAAH. Platelets were also incubated directly with 100 nM E2 or 100 nM E2-BSA. (B) Effect of various concentrations of AEA on [³H]5-HT release from human platelets, also in the presence of SR141716, SR144528, CBD, or CAPS, each used at 2 μM. The effect of 100 nM arachidonic acid (AA) or ethanolamine (Et-NH₂) was also investigated. (A-B) 100% = 300 ± 30 fmol/10⁹ platelets. (C) Effect of coincubation with HUVECs, untreated or treated with 100 nM E2, or of incubation with 100 nM E2, 100 nM E2-BSA, 100 nM E2 + 100 nM TMX, or 100 nM E2 + 100 nM ICI182780, on the levels of IP₃ and cAMP in human platelets (100% = 8.3 ± 1.0 or 1.2 ± 0.1 pmol × mg protein⁻¹ for IP₃ or cAMP, respectively). Values are reported as means ± SD. *P < .01 and **P < .05 compared with untreated control; #P < .01 and @P < .05 compared with E2-treated cells (P > .05 in all other cases).