DOBESILATE ENHANCES ENDOTHELIAL NITRIC-OXIDE SYNTHASE ACTIVITY IN MACROVASCULAR AND MICROVASCULAR ENDOTHELIAL-CELLS

1 Dobesilate is used for normalizing vascular dysfunction in a number of diseases. In search for an effect on endothelial NO production, mac rovascular endothelial cells from rat aorta, microvascular endothelial cells from rat exocrine pancreatic tissue, and capillary endothelial cells from rat islets, were cultured in the presence or absence of ME- Dobesilate. The activity of constitutive nitric oxide synthase (ecNOS) in resident cells as well as of inducible nitric oxide synthase (iNOS ) in cytokine-activated cells was measured indirectly by recording the citrulline concentrations in culture supernatants. 2 In each of the d ifferent endothelial cells Mg-Dobesilate incubation (0.25-1 mM) for 24 h led to a significant and concentration-dependent increase in ecNOS- activities, With cytokine-activated endothelial cell cultures only mod erate effects were seen with little or no concentration-dependency. Ad dition of the NOS-inhibitor N-G-monomethyl-L-arginine led to a signifi cant suppression of citrulline formation in all cultures as an evidenc e for the enzyme specificity of these effects. 3 iNOS- and ecNOS-speci fic reverse transcription and semi-quantitative polymerase chain react ion (RT-PCR) with RNA from resident or cytokine-activated endothelial cells gave no evidence for an increase in NOS-specific mRNA after ME-D obesilate-treatment. Furthermore, Dobesilate-mediated enhancement of N O synthesis in resting endothelial cells was not due to iNOS induction in these cells, as no iNOS-specific signal was found by RT-PCR.