Influence of chronic exposure to high concentrations of D-glucose and long-term beta-blocker treatment on intracellular calcium concentrations of porcine aortic endothelial cells.

Clinical observations indicate that diabetes leads to micro- and macroangiopathy involving endothelial dysfunction. Because recent studies indicate an antiangiopathic effect of celiprolol, but not of metoprolol, in type 1 diabetes, we investigated the direct influence of exposure to high D-glucose concentrations on endothelial cells and the possible effects of both beta-blockers. Nine different chronic treatments were carried out on cultured porcine aortic endothelial cells: 1) 5 mmol/l D-glucose ("normoglycemic" cells), 2) 5 mmol/l D-glucose plus 15 mmol/l L-glucose (osmotic control), 3) 5 mmol/l D-glucose plus 0.5 micromol/l celiprolol, 4) 5 mmol/l D-glucose plus 0.05 micromol/l metoprolol, 5) 5 mmol/l D-glucose plus 0.5 micromol/l celiprolol plus 5 micromol/l propranolol, 6) 20 mmol/l D-glucose ("hyperglycemic" cells), 7) 20 mmol/l D-glucose plus 0.5 micromol/l celiprolol, 8) 20 mmol/l D-glucose plus 0.05 micromol/l metoprolol, and 9) 20 mmol/l D-glucose plus 0.5 micromol/l celiprolol plus 5 micromol/l propranolol. Using the Fura-2 technique, application of either 1 nmol/l bradykinin or 1 micromol/l ATP to the normoglycemic endothelial cells led to a significant increase in intracellular calcium, whereas the hyperglycemic cells showed significantly less reactivity to both agents. Exposure of endothelial cells to L-glucose did not show any difference to normoglycemic controls. Coadministration of 20 mmol/l glucose and celiprolol demonstrated that the alteration of the calcium signal induced by high D-glucose concentrations could be significantly antagonized with celiprolol. In contrast, coincubation with metoprolol failed to normalize the calcium signal. This effect of celiprolol was completely abolished in the presence of propranolol. In normoglycemic cells, none of the beta-blockers influenced the intracellular calcium response to bradykinin or ATP. These results indicate that chronic treatment with high D-glucose concentrations leads to an impairment of calcium signaling, which might be ameliorated by celiprolol.