Stretch-induced morphological changes of human endothelial cells depend onthe intracellular level of Ca2+ rather than of cAMP

When exposed to a uni-axial cyclic stretch, cultured human umbilical vein e ndothelial cells (HUVECs) align and elongate perpendicular to the stretch a xis. Previous studies showed that forskolin inhibited stretch-induced orien tation of endothelial cells, suggesting that adenosine3:5-cyclic monophosph ate (cAMP) plays an important role in the shape change. However, we have re cently shown that stretch-induced shape changes in cultured HUVECs are due to increased [Ca2+],. In the present study, we examined the possible role o f cAMP in stretch-induced shape changes in cultured HUVECs, Application of uni-axial cyclic stretch induced a gradual rise in cAMP reaching a peak lev el at 60 min after the onset of stretch. The adenylate cyclase activator, f orskolin, increased the basal level of cAMP but inhibited the rise in [Ca2](i) resulting in no cell shape changes. In contrast, N 6,2-dibutyryladenos ine3:5-cyclic monophosphate (dbcAMP) enhanced the stretch-induced increase in cAMP and [Ca2+] and resulted in cell shape changes. On the other hand, 2 '5'-dideoxyadenosine (DDA), an adenylate cyclase inhibitor, inhibited stret ch-induced increases in cAMP and [Ca2+]i resulting in no cell shape changes . In summary, our data showed that cell shape changes were consistently dep endent on [Ca2+](i) rather than cAMP levels. We conclude that the primary s econd messenger in the stretch-induced shape changes in HUVECs is intracell ular Ca2+ rather than cAMP. (C) 2000 Elsevier Science Inc. All rights reser ved.