Ultrafiltration of plasma uric acid.

In view of the possibility that the uric acid of the blood might be partly "bound" to protein and partly "free" (Benedict and Behre, 1931) and that this might provide some explanation for the phases of gout, it was decided to investigate various methods of ultrafiltration of the plasma uric acid in gouty and normal individuals. Lambie (1940) reported a case of leukaemia with subsequent development of gout in which the ultrafiltrable fraction of the plasma uric acid was only 28%, but changed after splenectomy to normal, i.e., 100%. Lambie used collodion membranes for the ultrafiltration. His explanation was a change in the colloidal state of the blood urates. Adlersberg, Grishman, and Sobotka (1942) reviewed the literature on the solubility of uric acid, reporting Minkovski's view on the free and bound uric acid in body fluids and the different results hitherto gained by ultrafiltration of serum and plasma and the explanation given by the different authors. Adlersberg et al. ultrafiltered serum, using 80 lb. nitrogen per sq. in. (positive pressure) and a "600" cellophane membrane for 18 to 24 hours. They reported that in normal individuals 76-96% (average 84%) of the uric acid was filtrable. They claimed further that, in contrast to normal individuals, gouty patients show a considerable fluctuation in the uric acid partition, even when the total blood uric acid level remains constant. In three out of 10 gouty patients 80% was the average. Wolfson, Levine, and Tinsley (1947) used the anaerobic ultrafiltration method of Lavietes (1937), and found in normal individuals (13 filtrations in two patients) an ultrafiltrability of plasma uric acid of 79%. They used " 600 " cellophane membrane, which they soaked for three days at O' C. before use. Our first attempt was made with the positive pressure method of Adlersberg et al., but we found that we could not filter more than 20-30% of the uric acid, possibly because of shortcomings in our filtration arrangements. We therefore adopted the method of Lavietes, used by Wolfson and his colleagues, which is as follows.