Effects of chronic oral consumption of nicotine on the rabbit aortic endothelium

New Zealand white rabbits (10) were administered daily doses of nicotine (2.4 mg/kg/day) in their drinking water for 25 weeks. Nicotine-treated rabbits were compared with control rabbits (10) in terms of blood serum biochemistry and lipid profiles, blood cells counts, changes in aortic endothelial cell morphologic characteristic and distribution, and vessel wall permeability (Evans blue dye uptake). Fasting serum levels of glucose, triglycerides, total cholesterol, and LDL-cholesterol were elevated in nicotine-treated rabbits. No significant differences (nicotine vs control) were seen in leukocyte, erythrocyte and platelet counts, or hematocrit and hemoglobin. Control and nicotine-treated rabbit aortas showed similar focal areas of increased Evans blue dye uptake; staining was localized primarily to aortic arch areas. Endothelial cells (luminal surface) from non-Evans blue and Evans blue arch areas were examined by a combination of Häutchen preparation (silver-stained vessels) and scanning and transmission electron microscopy. Endothelial cells from nicotine-treated arch areas (Evans-blue-stained) showed extensive changes such as: increased cytoplasmic silver deposition, increased formation of microvilli, and numerous focal areas of "ruffled" endothelium (projections on cell surfaces). These data indicate that nicotine, administered orally to rabbits, has a demonstrable in vivo morphologic effect on endothelial cells in the aortic arch.