Influence of endothelial surface on flow velocity in vitro

The influence of the endothelial surface and its interaction with various plasma components on flow velocity was investigated in vitro. The falling velocity of microcarrier beads with and without cultured porcine aortic endothelial cells in a vertical tube containing different media was recorded with a video system attached to a light microscope. The falling velocity of the beads was in agreement with values predicted from Stokes's law. Endothelium did not affect the falling velocity in various media, except in plasma, where it was slower than expected. Fibrinogen was found to have a strong surface tension effect, disturbing viscosity measurements, and to bind to endothelial cells and collagen-coated surfaces. We conclude that the endothelial surface may interact with plasma and plasma constituents such as fibrinogen in a way that affects blood flow.