Transport pathways of low-density lipoproteins by arterial endothelium of hypercholesterolemic rats

Abstract

Atherosclerosis is more likely to occur at the branched regions of the large or mediumsized arteries. Physiological evidences show that changes in endothelial permeability at the branched regions can cause low density lipoproteins (LDL) to filtrate and accumulate in the intima. However, the LDL transport pathways across the arterial endothelium at the ultrastructural level still remain uncertain. The purpose of this experiment is utilizing fluorescein 1,1' -dioctadecyl-3,3,3',3' -tetramethylindocarbocyanine perchlorate (Dil) and colloidal gold as the tracer substances to investigate the transport pathways of LDL in the branched and the unbranched regions of arteries in the diet-induced hypereholesterolemic rats.Rat or human LDL was coupled to Dil or to 10-15nm colloidal gold particles according to the standard procedures. Male Srague-Dawley rats, weighing approximately 250 gm were fed high-cholesterol diets over a period of 12 months. At 6 and 12 months after feeding, animals were anesthetized by intraperitoneal injections of sodium pentobarbitol. The vascular bed was cleared of blood by perfusion with oxygenated PBS supplemented with 0.25% glucose and 1 mM CaCl2 at 37°C through the left ventricle. After the blood washed out, the right and the left femoral arteries and the left ventricle, the thoracic and the abdominal aorta were cannulated with polyethylene tubings. The tubings between the left ventricle and the thoracic aorta and the tubings between the abdominal aorta and the femoral arteries were connected with peristaltic pump to form two closed circuits.