Effect of D-glucose on nitric oxide release from glomerular endothelial cells

Background Altered glomerular production of nitric oxide (NO) may be involv ed in hyperfiltration in early diabetic nephropathy. However little is know n as to the role of glomerular endothelial cells (GECs) in diabetic hyperfi ltration and their ability to release NO in response to hyperglycemia. Methods Using an established cell line, we directly monitored NO release fr om GECs in response to various concentrations of D-glucose, D-mannitol, and L-arginine, an NO synthase (NOS) agonist. L-Arginine-induced NO release wa s examined in the cells pretreated for different periods up to 24 h with 10 or 30 mM D-glucose. We also measured serially the accumulation of nitrite, the stable metabolite of NO, produced by the cells incubated for up to 24 h under 10 or 30 mM D-glucose conditions in the presence or absence of the NOS inhibitor, L-NAME. Results Direct measurement of NO demonstrated that D-glucose, but not D-man nitol, stimulation resulted in a rapid and dose-dependent increase in NO re lease by the cells. However, L-arginine-induced NO release was attenuated s ignificantly in the cells preincubated for more than 12 h with 30 mM D-gluc ose compared to 10 mM D-glucose. The L-NAME-inhibitable production of nitri te in the media was significantly increased 1.5-2.0-fold until 6 h after in cubation with 30 mM D-glucose compared to 10 mM D-glucose. Conclusions We conclude that D-glucose, but not D-mannitol, produces a rapi d and dose-dependent increase in NO release, whereas exposure to high D-glu cose for more than 12 h may blunt NOS activity and/or NO stability in the G ECs. These observations may therefore be important for glomerular endotheli al dysfunction induced by hyperglycemia that is still tentative and may hav e a role in diabetic nephropathy. Copyright (C) 2001 John Wiley & Sons, Ltd .