Metabolism of rabbit angiostatin glycoforms I and II in rabbits: angiostatin-I leaves the intravascular space faster and appears to have greater anti-angiogenic activity than angiostatin-II.

Plasminogen (PLG) exists in the circulation as two glycoforms, I and II. Angiostatin (AST) is a polypeptide that has been cleaved from the kringle region of PLG and has strong anti-angiogenic properties. AST-I and AST-II, which consisted only of kringles 1 through 3, were prepared by the action of urokinase on purified rabbit PLG-I and PLG-II, respectively, in the presence of N-acetyl cysteine, followed by affinity chromatography on lysine-Sepharose. Purified AST-I and AST-II were tested for functional activity with a chick chorioallantoic membrane (CAM) model; when similar amounts were applied to a 6-day CAM, AST-I was substantially more effective than AST-II in decreasing vascular supply to the CAM over a 72-hour period; this activity correlated with a loss of capillaries, probably through apoptosis of endothelial cells. Radiolabeled AST-I and AST-II (iodine 125 and iodine 131) were co-injected intravenously into healthy rabbits to determine their clearances from plasma measured over 3 days. Over a dose range of 0.08 to 2.7 microg/kg, the fractional catabolic rate within the intravascular space (j(3)) indicated that AST-I was cleared 3-fold to 4-fold more rapidly than AST-II (P < .001). The catabolic half-life of AST-I (2.01 +/- 0.19 days) was significantly less than that of AST-II (2.62 +/- 0.20 days). The faster clearance of AST-I from the intravascular space was matched by its more rapid passage than AST-II to the extravascular space of various organs over 60 minutes in vivo. This property of AST-I as compared with AST-II may partially explain its greater anti-angiogenic potential. From the plasma concentrations of PLG-I and PLG-II and their relative behaviors toward rabbit VX-2 lung tumors in vivo, we predict that substantially greater quantities of AST-II than AST-I may be released into the extravascular space of tumors.

The procoagulant state of the VX-2 tumor in rabbit lung in vivo--relative accumulation of fibrinogen, prothrombin, plasminogen, antithrombin and heparin cofactor II within the tumor.

During their growth, many malignant solid tumors elicit a hemostatic response in the host. In this report, the fluxes of various rabbit plasma hemostatic proteins into pulmonary VX-2 tumors have been measured in vivo. VX-2 cells were contained within a small rabbit plasma clot which was injected intravenously into rabbits. At 28 d, each rabbit was injected intravenously with two radiolabeled (131I, 125I) proteins selected from fibrinogen, prothrombin, antithrombin-alpha, heparin cofactor II, or plasminogen-I or -II. After allowing the labeled proteins to circulate for 10-200 min, each rabbit was perfused with Krebs-Henseleit solution and the lungs excised. Solid tumors were isolated, weighed and measured for radioactivity content. A mean of 14 tumors/pair of lungs with a mean tumor weight of 0.3 g was obtained. Radioactivity per g of tumor was related to radioactivity/ml of blood at exsanguination for each protein at each time interval. Maximum flux rates were calculated (as pmol/g of tumor/min): Fibrinogen, 65.0; prothrombin, 53.0; antithrombin-alpha, 24.1; HCII, 17.2; plasminogen-II, 5.0; and plasminogen-I, 3.2. Using immunocytochemical staining, fibrin(ogen) was distributed heterogeneously within the VX-2 tumor, appearing largely in the perinodular region and in the necrotic core. From the net fluxes of these proteins, the profile of chronic hemostasis associated with the VX-2 tumor was shown to differ markedly from the hemostatic response that occurs after an acute vascular injury.

Endothelial adhesion molecule expression is enhanced in the aorta and internal mammary artery of diabetic patients.

BACKGROUND: Diabetes mellitus is a major risk factor for the development of atherosclerosis but the mechanisms involved remain unclear. The expression of leukocyte adhesion molecules at the endothelial surface is a primary step in the recruitment of leukocytes into the intima and the subsequent development of lipid-containing foam cell lesions. Increased levels of circulating adhesion molecules have been identified in diabetic patients, but the distribution in the arterial wall has not been described. MATERIALS AND METHODS: Frozen sections were prepared from aorta and internal mammary artery obtained during bypass surgery from 12 diabetic and 16 nondiabetic patients. Adhesion molecules (intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-Selectin), macrophages, and lymphocytes were identified and quantified using immunohistochemistry; intimal hyperplasia was quantified. RESULTS: Endothelial expression of VCAM-1 and intimal smooth muscle cell expression of both VCAM-1 and ICAM-1 was increased in the aortas from diabetic patients. Intimal hyperplasia in aorta and internal mammary artery sections was significantly greater in diabetic tissue. Macrophages, T-lymphocytes, oil-red-O-stained lipid, glycated albumin, and glycated LDL were observed in the aorta of both diabetic and nondiabetic samples. CONCLUSIONS: The increased incidence of VCAM-1 and ICAM-1 in the aorta may partly explain the enhanced atherosclerosis associated with diabetes mellitus, and their presence in established lesions may emphasize their long-term importance. The intimal hyperplasia observed in the bypass vessel may be a contributing factor to the increased incidence of restenosis in diabetic patients.