A role for pericellular proteoglycan in the binding of thrombin or antithrombin III by the blood vessel endothelium? The effects of proteoglycan-degrading enzymes and glycosaminoglycan-binding proteins on 125I-thrombin binding by the rabbit thoracic aorta in vitro.
Rabbit thoracic aorta segments were treated with either proteoglycan-degrading enzymes or with glycosaminoglycan-binding proteins to examine the nature of the endothelial and subendothelial binding sites of 125I-thrombin. Treatment (5-30 min) with enzymes (heparitinase, chondroitinases AC or ABC) caused a decrease in 125I-thrombin binding by the endothelium (30-70%) and by the subendothelial (intima-media) layer (20-50%); a low-specificity protease destroyed endothelial binding almost entirely and reduced binding to the subendothelium by approximately 60% over a similar period. Of the glycosaminoglycan-binding proteins, pretreatment of the aorta wall with protamine caused a 30% decrease in thrombin binding to the endothelium whereas lipoprotein lipase (present during 125I-thrombin uptake) decreased binding by up to 40%. Pretreatment with antithrombin III did not significantly affect binding of either 125I-thrombin or 125I-FPR-inactivated thrombin. In contrast to thrombin, 125I-antithrombin III was not readily uptaken by the aorta segments. These observations indicate that, whereas the minimal binding by 125I-antithrombin III probably does not involve endothelial proteoglycan, a strong case can be made for endothelial and subendothelial proteoglycan binding sites for thrombin.
D000345:Affinity Labels; D000818:Animals; D000990:Antithrombin III / Q000378:metabolism* / Q000494:pharmacology; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism*; D002808:Chondroitin Lyases / Q000494:pharmacology; D004727:Endothelium / Q000378:metabolism; D006025:Glycosaminoglycans / Q000378:metabolism*; D008071:Lipoprotein Lipase / Q000494:pharmacology; D008297:Male; D009842:Oligopeptides; D011133:Polysaccharide-Lyases / Q000494:pharmacology; D011402:Pronase / Q000494:pharmacology; D011479:Protamines / Q000494:pharmacology; D011509:Proteoglycans / Q000502:physiology*; D011817:Rabbits; D013462:Sulfur Radioisotopes; D013917:Thrombin / Q000378:metabolism*
D000345:Affinity Labels; D006025:Glycosaminoglycans; D009842:Oligopeptides; D011479:Protamines; D011509:Proteoglycans; D013462:Sulfur Radioisotopes; C020924:phenylalanyl-prolyl-arginine methyl chloride; D000990:Antithrombin III; D008071:Lipoprotein Lipase; D013917:Thrombin; D011402:Pronase; C022677:Streptomyces griseus neutral proteinase; D002808:Chondroitin Lyases; D011133:Polysaccharide-Lyases; C021349:heparitinsulfate lyase