We evaluated the influence of high ambient glucose on cellular expression of adhesion molecules, known to mediate endothelial interaction of leucocytes and monocytes. Paired cultures of individual isolates of human umbilical vein endothelial cells (HUVECs) were studied by fluorescence activated cell sorter analysis after exposure to 30 vs 5 mmol/l glucose. Incubation of HUVECs for 24h in 30 mmol/l glucose increased ICAM-1 (intercellular adhesion molecule-1; 116.4 +/- 16.9% of control, p < or = 0.05), but not PECAM (platelet endothelial cell adhesion molecule) expression, compared to cultures kept in 5 mmol/l glucose. Long-term exposure (13 +/- 1 days) of HUVECs to 30 mmol/l glucose increased expression of ICAM-1 to 122.5 +/- 32.2% (p < 0.002) and reduced that of PECAM to 86.9 +/- 21.3% vs the respective control culture in 5 mmol/l glucose (p < 0.02). Stimulation of confluent HUVECs, kept in 30 vs 5 mmol/l glucose for 13 +/- 1 days, with 20 U/ml interleukin-1 for 24 h (ICAM-1) and 4 h (endothelial leukocyte adhesion molecule 1) resulted in reduced ICAM-1 (84.8 +/- 27.0%, p < 0.05) and endothelial leukocyte adhesion molecule-1 (87.6 +/- 22.4%, p < 0.05) expression vs control cells, while that of PECAM (t:24 h) and vascular cell adhesion molecule-1 (t: 16 h) remained unchanged. In conclusion, it appears that differences in expression of adhesion molecules on HUVECs in response to high glucose reflects endothelial glucose toxicity, which may also induce endothelial dysfunction in diabetes.