EFFECTS OF AMRINONE ON THROMBIN-INDUCED PLATELET-DERIVED GROWTH FACTOR-LIKE PROTEIN SECRETION FROM ENDOTHELIAL-CELLS

Endothelial cells (EC) secrete platelet-derived growth factor (PDGF)-like protein, which is a potent mitogen to smooth muscle and connective tissue cells. The purpose of this study was to determine if amrinone, a phosphodiesterase inhibitor, could inhibit PDGF-like protein secretion on the basis of its ability to increase cAMP. Human umbilical artery endothelial cells (HUAEC) (n = 7) were preincubated for 4 h with amrinone (10-mu-g/mL) before coincubation with thrombin (10 IU/mL) and amrinone (10-mu-g/mL) for 18 h. The supernatant was then assayed for the presence of both PDGF-like protein by using a competitive I-125-PDGF radioreceptor inhibition assay, and cAMP by using an RIA. Thrombin-induced PDGF-like protein secretion from HUAEC was significantly inhibited by amrinone (7.8 +/- 1.6 fmol/10(6) EC) when compared with thrombin alone (12.1 +/- 2.4 fmol/10(6) EC) (p < 0.05). Amrinone alone had no effect on baseline PDGF-like protein secretion. Amrinone inhibition of thrombin-induced PDGF-like protein secretion was comparable whether amrinone was added to HUAEC 4 or 0 h before thrombin, and it was dose dependent with a maximal inhibition of 82.7% by amrinone (160-mu-g/mL). In contrast, IL-1-alpha (10-mu-g/mL) and tumor necrosis factor (100 ng/mL) induced less secretion of PDGF-like protein from HUAEC, and this secretion was not inhibited by amrinone. Amrinone (10-mu-g/mL) significantly increased secretion of cAMP from HUAEC from a baseline value of 6.4 +/- 0.4 pmol/10(6) EC to 10.6 +/- 0.1 pmol/10(6) EC (p < 0.01). We conclude that amrinone inhibits thrombin-induced PDGF-like protein secretion from HUAEC. This ability of amrinone to inhibit thrombin-induced PDGF-like protein secretion from EC is associated with an increase in secretion of cAMP from EC, suggesting that this inhibition is associated with, or mediated through, an increased production of cAMP.