Diffusion-weighted MR imaging in hypertensive encephalopathy: clues to pathogenesis |
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Authors: | RB Schwartz RV Mulkern H Gudbjartsson F Jolesz |
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Affiliation: | Institut für Pharmakologie und Toxikologie, Karl-Franzens-Universit?t Graz, Austria. kurt.schmidt@kfunigraz.ac.at |
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Abstract: | We investigated the effects of organic buffers on the NO-like biological activities of ONOO-. In HEPES buffer (50 mM), ONOO- (1 mM) induced a 20-fold increase in endothelial cGMP accumulation and the effect was comparable to that elicited by a maximally active concentration of the NO donor DEA/NO. ONOO- produced a 12-fold increase of cGMP in MOPS buffer (50 mM), but was virtually inactive in phosphate buffer (50 mM). Electrochemical detection of NO showed that the biological effects of ONOO- in HEPES or MOPS were due to accumulation of compounds that released NO in the presence of copper ions. CuCl2-induced formation of NO was completely blocked by the Cu(I) chelator neocuproine but unaffected by the Cu(II) chelator cuprizone, pointing to a Cu(I)-catalyzed decomposition pathway. Formation of NO from ONOO- was not detectable in phosphate buffer, in agreement with the lack of effect of ONOO- on cGMP accumulation in this buffer. These data demonstrate that certain buffer components present in cell culture media may yield artificial results in experiments with authentic ONOO-. |
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