The effect of low-speed agitation on the level of secretion and glycosylation patterns of the Von Willebrand factor in endothelial cells cultured in 6-cm Petri dishes located in a rotating platform was studied. In this simple system, complex and non-intuitive velocity fields arise. As revealed by simple calculations of tangential velocities and CFD analysis, flow behavior strongly varies as a function of radial distance and rotational velocity. We found significant differences in both secretion level and glycosylation extent and completeness, as a result of relatively small changes in rotational speed. Results obtained support the hypothesis that differences in hydrodynamic conditions may induce important changes in the secretion and assembly of glycoproteins in mammalian cell cultures. (C) 2009, The Society for Biotechnology, Japan. All rights reserved.