Colloid Osmotic Pressures of Serum Proteins in Nephrosis and Cirrhosis: Relations to Electrophoretic Distributions and Average Molecular Weights

Abstract

In the course of a series of direct osmotic pressure measurements on individual sera of nephrotic children undergoing spontaneous diuresis induced by measles, simultaneous detns. of protein N,electrophoretic distr., and protein specific refractive increments were carried out on a small group of sera, in order to see whether, with the most accurate possible use of the electrophoretic technique, a recently proposed relation for osmotic pressure of normal pooled plasma in terms of albumin and globulin levels can be applied. Results indicate that the relation gives a good correlation with measured pressures in the low pressure range, but in the intermediate range the predicted pressures are much lower than the measured and the discrepancies much larger than the reproducibility of the osmotic pressure method. In a series of sera and ascitic fluids of cirrhotic patients studied by uncorrected electrophoresis, predictability of measured osmotic pressures proved to be not much better. In serial sera from a patient with severe cirrhosis showing clinical improvement, osmotic pressure doubled without significant shifts in serum levels of electrophoretic components. No evidence for significant quantities of unusually large non-lipid bearing globulin molecules, or of dissociation of larger complexes with dilution, could be obtained from intercepts or slopes of pressure/concn. vs. concn. plots in a small group of water-logged cirrhotic patients. Avg. molecular wts. predicted from normal wts. of electrophoretic albumins and gamma globulins, together with the distrs. for certain disease states, proved to be only slightly higher than measured avg. molecular wts. of the proteins of these sera. Similar plots of sera from nephrotic patients gave evidence of high avg. molecular wts. (range 160,000 to 830,000) varying with the stage of the syndrome. There was no evidence of dissociation of such aggregates with dilution. These plots did not disclose, but do not rule out, the existence of proteins of unusual osmotic properties as suggested by osmotic edema.