GENERATION OF NITRATE DURING DIALYSIS AS A MEASURE OF NITRIC-OXIDE SYNTHESIS

Nitric oxide (NO) is a recently identified messenger, which influences the local regulation of blood flow and platelets as well as neuronal and inflammatory pathways. Disturbed NO information might be involved in the uremic syndrome and might also cause hypotension during dialysi s. To clarify these issues, we analyzed plasma and dialysis fluid conc entrations of nitrate, the stable NO metabolite, in 9 patients during hemodialysis. Plasma nitrate was raised at the onset of dialysis as co mpared with healthy subjects (83 +/- 9 versus 26 +/- 2 mu mol/L). The plasma concentration decreased to 20 +/- 2 mu mol/L. (p < 0.01) during the dialysis. The relative decrease was more pronounced than the rela tive reduction in creatinine, phosphate, and urea concentrations. A pa rallel decrease in nitrate was seen in effluent dialysis fluid (32 +/- 4 to 14 +/- 1 mu mol/L; p < 0.01). Calculations of the amount of nitr ate coming to and from the dialyzer were performed in 7 of the 9 patie nts, and in 5 of the 7 patients, generation of nitrate within the dial yzer could be postulated. This might explain the paradoxical venodilat ion noted during hemodialysis.