Fractionation of the Serum and Plasma Proteins by Salt Precipitation in Infants and Children. 1. The Changes With Maturity and Age. 2. The Changes in Glomerulonephritis. 3. The Changes in Nephrosis1

Abstract

The various components constituting the plasma protein complex have been characterized by many different chemical methods. Perhaps the most extensively used method of defining the component proteins has been by describing their solubility behavior in salt solutions. Thus, the terms fibrinogen, euglobulin, pseudoglobulin, and albumin have been applied, not to molecular species or chemical entities, but to the fractional parts of the total plasma protein complex, separated by precipitation at specified salt concentrations.In this study, the plasma protein fractions "salted out" by increasing concentrations of salt solution were quantitated in normal infants and children. The influence of maturity and age upon the concentration of the individual fractions precipitated was studied by examining and comparing the bloods of premature infants, full-term newborn infants, older infants, and children. The quantitative changes occurring during the course of various diseases, especially nephritis and nephrosis, were measured. METHODSThe phosphate salt mixture used by Butler et al. (1,2) in their study of the solubility curves of human plasma proteins was employed. These authors, using an equation derived by Cohn (3), obtained a discontinuous curve when the solubility of the protein expressed logarithmically was plotted against increasing concentrations of the phosphate precipitant. They stated that the breaks in the discontinuous curve were caused by successive precipitation of the progressively more soluble protein fractions.Briefly, the method entailed precipitation of the proteins at room temperature with increasing concentrations of a phosphate solution. The phosphate precipitant was made of equal parts of monobasic and dibasic potassium phosphate, so that the pH of the different concentrations employed was constant at 6.5. Blood was collected without I Aided by a grant from the Mead Johnson Company, Evansville, Indiana. stasis and allowed to clot. After centrifugation, the serum was separated. One volume of serum was added to 30 volumes of phosphate precipitant. (The different concentrations of phosphate precipitant were prepared from a stock 3 molar solution.). In actual practice, 0.2 cc. of serum was added to 6.0 cc. of phosphate solution; instead of filtrations as practiced by Butler et al. (1, 2), the precipitated protein was removed by centrifugation at 2,000 R.P.M. for 15 minutes in the angle centrifuge. Supernatant fluids were analyzed by the micro-Kjeldahl method. The concentrations of phosphate precipitant used with each serum ranged from 0.8 molar to 3.0 molar.Because there is, as indicated by Butler et al. (2), a lack of sharp breaks in the solubility curve of the serum proteins obtained by salt precipitation, we have recorded the absolute amount of protein (grams per 100 cc.) precipitated by each successive increase in salt concentrations of precipitant. In the interest of consistency, we have also designated in our tables the fractions precipitated by the Na,SO4 method of Howe (4)

Protein Requirements of Infants: 3. The Nutrition of Premature Infants

“…The globulin levels were relatively lower as a percentage of the full-term infants' levels than the albumin levels. These low levels confirm the observations made by Darrow and Cary (1933) and by Rapoport, Rubin, and Chaffee (1943). Other previous observers (Utheim, 1920;Bridge, Cohen, and McNair Scott, 1941;Hickmans, Finch, and Tonks, 1943) have found that the serum protein levels of premature infants are lower than those of full-term infants in the early weeks of life, but few details regarding the weight at birth and none about the diet of the infants are given in their reports.…”

Protein Requirements of Infants: 4--Serum Protein Concentrations in Normal Full-Term Infants

“…2.--Average serum protein levels in present series compared with the levels obtained by Trevorrow et al(1941),Darrow and Cary (1933),and Rapoport et al (1943)…”

The Electrophoretic Analysis of Maternal and Fetal Plasmas and Sera

“…The electrophoretic method yields the additional information that the concentration distribution of the individual globulins is quite different in the two types of material. Although poor in total globulin, the fetal samples are relatively rich in the presumably antibody-containing y globulin, the fetal values of P,/PG, 2 Although there is some evidence (15) that the solubility of the a, component corresponds to that of an albumin, it has been classified here as a globulin. When this component was first reported (6), the author did not state explicitly that it was a globulin but the terminology he suggested implied that he considered it to belong in this class of proteins.…”