[Effect of dialytic treatment and the relation between erythrocyte urea and plasma urea]

The existence of an intraerythrocytic binding between haemoglobin and urea is known; it determines, in normals, a higher erythrocyte than plasma urea concentration; this binding, in vitro, is progressive for an urea concentration range of 10-400 mg/dl. The only data found relating to dialysis patients, are reported by Nolph et al.; they indicate a decrease in the plasma-blood urea ratio during the blood transit through the dialyzer and a different ratio in comparison with normals, but in our opinion the method used to measure urea concentration was unsuitable. We determined urea distribution ratios by measuring, in blood and plasma, water and urea concentration in uremic inflow and outflow blood samples during dialysis. Our data indicate 1) an increase in outflow erythrocyte water (H2Oe inflow: 0.659, H2Oe outflow: 0.671 P less than 0.01) induced by a different erythrocyte osmotic gradient; 2) a not different ratio between urea of erythrocyte water and urea of plasma water in inflow and outflow samples of dialysed patients and in normals (respectively 1.06, 1.16, 1.13 p = n.s.). Our data from normal and uremic patients are like those found by Murdaugh & Doyle and by Colton & Lowrie in normals.