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The objective of this study was to determine Key words: nitric oxide; biocompatibility; dialysisintradialytic blood levels of nitric oxide (NO), membranes; electron paramagnetic resonancein patients undergoing chronic haemodialysis. Thiswas done by detection of nitrosylhaemoglobinby a sensitive technique of spin trap electron paramag- Introduction netic resonance at 0, 5, 15, 60, 180 and 240 minof a 4-h standard bicarbonate dialysis, using the same Vascular endothelial cells [1] and several other celldose (6000 U) of heparin and different dialysis mem- lines, including phagocytes [2], synthesize and releasebranes. The study group included 12 patients treated nitric oxide (NO). NO counterbalances the vasocon-with cellulose-derived dialysis membranes (nine with strictor action of endothelin (ET-1) and inhibits ET-1cuprophan and three with cellulose triacetate) production via a cGMP-dependent pathway [3,4].and 10 patients treated with synthetic membranes (five Evidence of a role for NO in diverse physiologic andpathologic processes is emerging [2]. The capability ofwith polysulfone and five with polymethylmethacryl-this molecule to oxidize critical compounds, i.e. thiols,ate). Control groups included 11 normal subjectshaeme groups and iron sulphurs, sustains its involve-and six patients with end-stage renal failure who werement in different biological processes. Besides vasodil-receiving intermittent peritoneal dialysis. Basal bloodatation, its functions include inhibition of plateletlevels of nitrosylhaemoglobin in haemodialysis patientsaggregation and modulation of inflammatory andwere significantly higher than normals, but similarimmune processes [2,5,6].to peritoneal dialysis patients. A significant increase Plasma concentrations of arginine, the endogenous(P

The role of vascular phenomena taking place during an attack of migraine are poorly understood. The aim of this study was to measure systemic levels of nitric oxide and endothelin-1, two of the most potent vasoactive mediators known, and to assess vasomotor responses through transcranial Doppler ultrasound monitoring in patients suffering from migraine without aura, both during the headache event and in headache-free periods as well as after pharmacologically induced pain relief. Seven patients (mean age 31.3 years, range 24 to 49 years), five women and two men, were enrolled in the pilot study. Transcranial Doppler recordings were performed according to conventional procedure. Endothelin-1 concentrations were measured by means of radioimmunoassay, whereas nitric oxide levels were estimated using electron paramagnetic resonance spectroscopy. Ultrasound evaluation did not show significant changes during migraine attacks compared to the interictal condition. Nitric oxide levels showed only slight differences between basal and attack conditions (0.85 +/- 0.46 versus 1.56 +/- 0.88, expressed as arbitrary units), and were raised after pharmacological intervention (2.91 +/- 1.93, P < 0.05). Plasma endothelin-1 concentrations decreased during migraine attacks with respect to interictal conditions (3.99 +/- 1.21 pg/mL versus 4.23 +/- 1.19), and returned to basal values (4.44 +/- 1.08 pg/mL) after relief of pain. Coupling the measurements of systemic levels of nitric oxide and endothelin-1 with transcranial Doppler velocity results will provide useful information on the hemodynamic changes of cerebral blood flow regulation in migraineurs, thereby adding new insights into the mechanisms of the migraine attack.