EPR DETECTION OF ENDOGENOUS NITRIC-OXIDE IN POSTISCHEMIC HEART USING LIPID AND AQUEOUS-SOLUBLE DITHIOCARBAMATE-IRON COMPLEXES

Spin-trapping techniques combined with electron paramagnetic resonance (EPR) spectroscopy to measure nitric oxide (. NO) production were com pared in the ischemic-reperfused myocardium for the first time, using both aqueous-soluble and lipophilic complexes of reduced iron (Fe) wit h dithiocarbamate derivatives. The aqueous-soluble complex of Fe and N -methyl-D-glucamine dithiocarbamate (MGD) formed MGD(2)-Fe-NO complex with a characteristic tripler EPR signal (a(N) 12.5 G and g(iso) = 2.0 4) at room temperature, in native isolated rat hearts following 40 min global ischemia and 15 min reperfusion. Diethyldithiocarbamate (DETC) and Fe formed in ischemic-reperfused myocardium the lipophilic DETC2- Fe-NO complex exhibiting an EPR signal (g(perpendicular to) = 2.04 and g(parallel to) = 2.02 at 77K) with a triplet hyperfine structure at g (perpendicular to) Dithiocarbamate-Fe-NO complexes detected by both tr apping agents were abolished by the . NO synthase inhibitor, N-G-nitro -L-arginine methyl ester. Quantitatively, both trapping procedures pro vided similar values for tissue . NO production, which were observed p rimarily during ischemia. Postischemic hemodynamic recovery of the hea rt was not affected by the trapping procedure.