Fibronectin Synthesis by Aorta Explants from Rabbits Fed High Cholesterol Diets

Abstract

Fibronectin synthesis was studied in aorta explants in culture from rabbits fed a high fat-high cholesterol diet. [³H]Mannose and [¹⁴C]leucine were used to label oligosaccharide side chains and the protein core, respectively. The synthesis was followed by monitoring immunoprecipitable fibronectin from the culture medium using polyclonal goat anti-rabbit fibronectin antibody. Synthesis of fibronectin increased by [¹⁴C]leucine (81%) and [³H]mannose (29%) incorporation over controls. On gel filtration, fibronectin synthesized by controls and cholesterol-fed rabbit resolved into four fractions. Pulse-chase experiment with [³H]glucosamine or [³H]leucine showed that fibronectin secreted by the aorta explants from rabbits fed high fat-high cholesterol diets incorporated an increased amount of radioactivity. Pulsing with [³H]mannose showed decreased incorporation of the label. During the chase period, the rate of secretion of fibronectin into the media by the hypercholesterolemic rabbit aorta explants was increased. The fibronectin that bound to the gelatin or heparin columns from cholesterol-fed rabbit aorta media had lower levels of [³H]mannose incorporated into the glycoprotein than the control. These results indicate that there is an alteration in carbohydrate composition of the fibronectin synthesized by the aorta explants from rabbits fed a high cholesterol diet. High fat-cholesterol intake could play a causative role in matrix dysfunction during atherogenesis by altering glycoprotein synthesis.