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1Department of Cell Biology and Genetics, University of North Texas Health Science Center, Fort Worth, Texas 76107; and 2Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202
Submitted 12 January 2004 ; accepted in final form 5 May 2004
Kidney glomeruli are important targets of diabetic nephropathy. We hypothesized a high concentration of glucose could suppress glomerular endothelial nitric oxide synthase (eNOS) by a protein kinase C (PKC) mechanism, as has been found in other tissues. Mouse kidney slices (150200 µm) were bathed in Hanks' solution with 100 µM L-arginine and exposed to either 5 or 2030 mM D-glucose. Immunofluorescence identified only eNOS in normal mouse glomeruli. Measurements of glomerular NO concentration with NO-sensitive fluorescent dye (4,5-diaminofluorescein diacetate) using confocal microscopy and NO-sensitive microelectrodes verified that resting glomeruli had active production of NO that was inhibited by NG-nitro-L-arginine methyl ester. High-concentration (2030 mM) D-glucose inhibited 6070% of the NO production within 1530 min; L-glucose at the same concentration did not have any effect. Inhibition of PKC-
with 100 nM ruboxistaurin prevented eNOS suppression in high-glucose media. Activation of PKC with 100 nM phorbol ester also suppressed the glomerular NO concentration. We concluded that eNOS in the renal glomerular capillary endothelial cells is suppressed by activity of PKC at high-glucose concentrations comparable to those in diabetic animals and humans. The consequence is a rapid decline in the generation of NO in the glomerular endothelial cells in the presence of a high concentration of glucose.
microelectrode; hyperglycemia; confocal imaging; protein kinase C; endothelial nitric oxide synthase
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