Inhibition of vascular smooth muscle cell growth by endothelial cell-derived heparin. Possible role of a platelet endoglycosidase.
Bovine aortic endothelial cells release a heparin-like substance in the presence of 0.4% fetal calf serum. This substance inhibited the growth of smooth muscle cells in vitro by about 70%. Substitution of platelet-poor plasma for serum resulted in minimal liberation of inhibitory activity from the cells unless at least 10-fold higher concentrations of platelet-poor plasma were utilized. This suggested that a platelet product was involved in the release process. Therefore, we examined the ability of the platelet heparitinase described in the preceding communication to release heparin-like species from cultured endothelial cells. Our results show that when endothelial cells were exposed to serum-free medium containing 1 ng/ml of the purified platelet endoglycosidase, at least as much inhibitory activity was released as was obtained with 0.4% serum. Dose response experiments indicated that only 10 pg/ml of the enzyme were necessary to liberate 50% of the inhibitory activity from endothelial cells. The heparin-like nature of the inhibitory substance was demonstrated by its sensitivity to Flavobacterium heparinase. Utilizing appropriate controls, the release of heparin-like material by the endoglycosidase was shown to be enzyme-specific and was not due to artifacts of experimental manipulations. In addition, this enzyme did not convert prereleased material to an active component, but directly liberated the active heparin-like species from endothelial cells. A simple model describing the possible role of heparin-like components and the endoglycosidase in the normal and injured wall is presented.
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000502:physiology*; D001792:Blood Platelets / Q000201:enzymology*; D002417:Cattle; D002455:Cell Division; D002478:Cells, Cultured; D006493:Heparin / Q000302:isolation & purification / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D011133:Polysaccharide-Lyases / Q000097:blood*; D051381:Rats
D006493:Heparin; D011133:Polysaccharide-Lyases; C021349:heparitinsulfate lyase