Cyclic AMP increases thrombomodulin expression on membrane surface of cultured human umbilical vein endothelial cells

Dibutyryl-cyclic AMP (Bt2cAMP; final concentration 1-5 mM) or beraprost sodium (synthetic prostacyclin, 100 nM) enhanced the expression of thrombomodulin (TM; an anticoagulant factor of endothelial cells) on the membrane surface of cultured human umbilical vein endothelial cells up to 1.4 times over the control within 9 hrs after the treatment, while the expression fell below the control level at 12 hrs and thereafter. 8-Bromo-cAMP (final concentration 1-5 mM) or 3-isobutyl-1-methylxanthine (IBMX; an inhibitor of phosphodiesterase; final concentration 10-1000 microM) enhanced the expression of TM on the cell surface at 12 hrs after the treatment. The enhancement of TM expression caused by Bt2cAMP was inhibited by incubation with phorbol 12-myristate 13-acetate. These results suggest that cAMP stimulates expression of TM in the endothelial cells.