FACTORS INDUCING CODISTRIBUTION OF MARGINAL ACTIN FIBERS AND FIBRONECTIN IN RAT AORTIC ENDOTHELIAL-CELLS

Rat endothelial cells have a unique arrangement of actin fibers runnin g with subendothelial fibronectin along the cell margins. The present study was conducted to identify the factors that are associated with c odistribution of these actin fibers and fibronectin in fetal rat aorti c endothelial cells, mainly using rheological techniques. Fluorescence histochemistry revealed that the codistribution pattern was establish ed between gestational days 14 and 15. The endothelial cells changed f rom polygonal to spindle shaped during this gestational period. Althou gh the aortic length remained almost unchanged during this period of g estation, both the diameter and expansion ratio of the aorta increased , by 9 and 10%, respectively. On the other hand, the wall shear rate i ncreased rapidly during gestational days 13-16. These results indicate that the codistribution of actin fibers and subendothelial fibronecti n along the margins of endothelial cells in fetal rat aorta occurs in association with a rise in stretch and shear stress and that the endot helial cells may require this change to maintain structural integrity.