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Background: Avian tuberculosis is an important disease affecting all species of birds and is most often caused by Mycobacterium avium or Mycobacterium genavense. Blood proteins are important diagnostic constituents in gastrointestinal, hepatic, renal, and infectious diseases., Objective: The aim of the study was to compare serum protein profiles of domestic pigeons (Columba livia var. domestica) infected with Mycobacterium avium subsp. avium (MAA), with healthy pigeons., Methods: Serum samples were collected from 80 pigeons with clinical signs of tuberculosis, all kept in the same loft. All birds were necropsied and cultured for mycobacteriosis; positive cultures were typed for MAA by PCR reactions targeting 16S rRNA, IS901 and IS1245. The concentration of total serum proteins was determined by the biuret method and spectrophotometry. Individual protein fractions were analyzed by cellulose acetate electrophoresis and extrapolated based on total protein concentration. For statistical analysis, the infected birds were compared with healthy pigeons., Results: A total of 37 pigeons with culture results positive for MAA were selected and allocated to 2 groups, a culture-positive group with macroscopic lesions of tuberculosis and another without macroscopic lesions. Six protein fractions were identified: prealbumin, albumin, alpha-1, alpha-2, and beta globulins and gamma globulins. Concentrations of total protein, beta globulins and gamma globulins were statistically significantly higher in the infected pigeons when compared with the control group. There were no significant differences between the groups of birds with or without macroscopic lesions., Conclusions: Statistically significant differences in total protein, and beta and gamma globulin concentrations in all infected pigeons suggest that serum protein electrophoresis represents a nonspecific but valuable indicator for tuberculosis in pigeons., (© 2013 American Society for Veterinary Clinical Pathology.)

Background: Contemporarily, food production without food additives is very rare. Increasingly often, however, scientific works report on adverse effects of specified, single food additives on the body. Data is, in turn, lacking on the synergistic effect of a mixture of different food additives on body functions and its main metabolic pathways., Objective: The objective of this study, an animal model, was to evaluate if and in what way the compound of chosen and most frequently used and consumed food additives, along with the change of diet composition to processed, purified, influence the selected markers of protein metabolism., Material and Methods: The animals were divided into four groups, which were fed with compound of feed pellets: group I and II with basic compound, group III and IV with modified compound in which part of the full grain was replaced by isocalorie wheat flour type 500 and saccharose. Animals from groups I and III received tap water, which was standing for some time, to drink. Animals from groups II and IV received solution of chosen additives to food and next they were given water to drink. The amount of given food additives was evaluated by taking into consideration their consumption by people recalculated to 1 kg of their body mass. The experiment spanned for 7 weeks., Results: It was ascertained that the applied additives caused significant changes in total protein concentration and its fractions: albumin, alpha1-globulin, alpha2-globulin, beta-globulin and gamma-globulin in the blood serum of the animals under research, which can indicate and contribute to disclosure of creation of undesirable food reaction, especially when recommended levels of consumption of those additives are being exceeded. The organism response to the applied additives and accompanying it change of diet was essentially connected to sex of the animals. Undesirable character of changes taking place under the influence of applied additives, was observed both in animals fed with basic feed and modified feed with various intensity according to the parameter under research., Conclusions: The analysis of the results achieved enabled concluding that the applied mixture of food additives caused significant changes in the concentration of total protein and its fractions: albumins, alphal-, alpha2-, beta- and gamma-globulins in blood serum of the investigated animals. These changes may indicate but also may contribute to the development or manifestation of undesirable nutritional responses, especially when recommended dietary allowances are exceeded. The body's response to the applied additives and concomitant modification of diet composition was significantly correlated with sex of the animals. The unfavorable character of changes following the administration of additives was observed in both the animals on the basal diet and these fed the modified feed mixture, yet with a different intensity that was found to depend not on the feeding group but on the parameter examined.

The aim of this study was to evaluate the effect of blood withdrawal on the plasma volume and serum proteins concentration during incremental cycling exercise test performed 24 hours after blood donation (withdrawal of 450 ml of blood). Thirteen subjects (mean +/- SD), age 23 +/- 3 years; body mass 75 +/- 10 kg; BMI 23.4 +/- 2 kg.m-2; VO2max 2903 +/- 334 ml.min-1, performed an incremental cycling exercise test, starting at the power output of 20 W with an increase by 20 W every 3 minutes--until exhaustion. This test was performed twice: once in the control study (7-12 days before blood donation) and repeated 24 h after blood donation. The blood for this study was taken from the antecubital vein, in a sitting position at rest (6 minutes before the exercise test, at the end of the test (the stage of exhaustion) and 2 hours after the end of the test. The changes in plasma volume were evaluated on the basis of changes in hemoglobin and haematocrit concentrations. Significances of differences in the studied variables were tested using Wilcoxon test. At the end of the exercise test a significant (p < 0.05) decrease in plasma volume was found in both study. It amounted to -11.1 +/- 2.9% in the control study, and to -13.0 +/- 3.9% after blood donation. The difference in the changes in plasma volume in both tests was not significant. In the control study plasma volume return to the pre-exercise value within 2 hours after the end of the exercise test. In the study performed after blood donation the values of plasma volume exceeded the control value by 3.9 +/- 6.7% (p < 0.05) within 2 hours after finishing the exercise test. Taking into consideration the changes in plasma volume it was found that during incremental exercise there is a significant (p < 0.05) extra vascular escape of the serum proteins both in the control study, in case of total serum protein amounting to 4.05 +/- 2.97 g.l-1 as well as during exercise performed after blood donation, amounting to 5.49 +/- 3.98 g.l-1. Moreover, it was found that in the control study all the measured serum proteins concentrations (albumin, alpha 1-, alpha 2-, beta-, and gamma-globulins) return to the pre-exercise level within 2 hours after the end of exercise, but in the study performed after blood donation a continuous extra vascular escape of some serum proteins (alpha 1-, alpha 2- and gamma-globulins) was observed.

The binding affinity of various trace elements to blood components and the pH-dependence of the binding affinity of the elements to serum proteins were examined using the radioactive multitracer technique. The binding affinity of 13 elements (Be, V, Mn, Zn, Se, Rb, Sr, Ce, Eu, Gd, Tm, Yb, and Lu) was simultaneously determined by gamma-ray spectrometry. The blood drawn from rats was separated into plasma, corpuscles, and erythrocyte ghosts. It was found that Be, Sr, Mn, and Zn bind highly to the plasma proteins. V and Se were highly bound to the corpuscles, and Se to the erythrocyte ghosts as well. Similar binding percentages of rare earth elements (Ce, Eu, Gd, Tm, Yb, and Lu) were found for each of the blood components, with the highest percentages being observed for plasma proteins. Albumin, beta-globulin, gamma-globulin, apotransferrin, and holotransferrin were examined in the study on the affinity of individual serum proteins. The pH dependence of the affinity of metal ions to the serum proteins in the pH range of 6.4-8.5 was examined using ultrafiltration and gamma-ray spectrometry. Each element showed a characteristic binding affinity to each serum protein, depending on pH. The results are discussed in terms of the chelating ability of metal ions and the nature of the serum proteins.

The effects of fumonisin B1 (FB1) intoxication in chickens were evaluated in three experiments. Two-day-old broiler chicks were fed a diet containing 10 mg pure FB1/kg feed for 6 days; some chicks were necropsied at this time, and others were allowed to recover for 5 wk before necropsy. In two other experiments, 2-day-old chicks were fed a broiler starter ration prepared with Fusarium moniliforme culture material containing FB1; one group received 30 mg/kg for 2 wk, and another received 300 mg FB1/kg for 8 days. Compared with controls, intoxicated chicks exhibited decreased prothrombin time, increased plasma fibrinogen (not included for the group receiving 30 mg/kg of culture material), and increased antithrombin III activity. Simultaneously decreased serum albumin concentration and increased serum globulins could be observed in groups intoxicated with F. moniliforme culture material containing FB1. The group allowed to recover for 5 wk did not exhibit modifications in hemostasis or serum proteins compared with controls. The results indicate that low doses of pure FB1 (10 mg/kg) and FB1 from F. moniliforme culture material (30 mg/kg) may alter hemostasis and serum proteins in young chicks.

Physiologic variations are known to develop in milk and serum proteins of women during lactation. This study was intended to evaluate whether modifications of the major serum proteins and alpha, beta, and gamma fractions occur during lactation in Macaca fascicularis. The alpha 1 and gamma globulins decreased and the alpha 2 and beta globulins increased; results of specific protein determinations indicated a decrease in almost all globulins. The protein trends during lactation in M. fascicularis are probably modified by estrogen and progesterone variations after delivery. Estrogen trends are similar in women and cynomolgus monkey females, whereas progesterone patterns between women and female macaques are different during the postpartum period.

Quantitive estimations of serum proteins, including Alpha 2M globulin, from 34 patients suffering from craniocerbral trauma have been carried out. The mean value curves over a period of two weeks following trauma are presented graphically. After severe injuries, depending on the size of the cerebral lesions, an increase in Alpha 2 of prognostic significance has been observed. Levels of Alpha 2M do not correlate directly with Alpha 2 globulin, and tend to fall initially. Falls in the first three days after injury may be prognostically significant from the point of view of the prediction of a lethal outcome. There are no significant changes in the levels of total protein, albumin, Beta globulin or Gamma globulin, but Alpha 1 globulin follows the curve of Alpha 2, although to a less marked degree. Correlations between serum protease activites and increases in Alpha 2 due to enzymatically active complexes are unconnected with Alpha 2M, a decrease in which indicates increased inhibitor activity and exhaustion of the inhibitor system.

Using the constant fusion and single injection technique the metabolic clearance rates (mean +/- SEM) for delta5-androstene-3beta, 17beta-diol (delta5-idol) were measured for 19 normal men (1311 +/- 67 1/24 h) and 10 normal women (858 +/- 63 1/24 h). The constant infusion technique yielded values for the conversation ratios for the transformation of delta5-diol to several products: dehydroepiandrosterone (DHEA)/delta5-diol of 0.06+/-0.01 for men and 0.05 +/- 0.01 for women, of delta5-diol sulfate/delta5-diol of 0.45 +/- 0.04 for men and 0.52 +/- 0.03 for women and of DHEA sulfate/delta5-diol of 5.53 +/- 0.26 for men and 5.02 +/- 0.42 for women. The single injection technique yielded rate constants (units) and volumes of distribution (liters) for delta5-diol; Ki = 34.3 +/- 4.3 for men and 35.0 +/- 3.9 for women, K2 = 63.7 +/- 4.1 for men and 75.1 +/- 4.2 for women, V1 = 23.1 +/- 3.2 for men and 11.9 +/- 2.3 for women, V2 = 14.8 +/- 3.7 for men and 9.2 +/- 3.2 for women. The mean delta5-diol plasma concentration was 1.08 +/- 0.10 ng/ml for 12 men and 1.17 +/- 0.16 ng/ml for 9 women. (he calculated blood production rates for delta5-diol were 1357 +/- 117 mug/24 h for 12 men and 969 +/- 131 mug/24 h for 9 women. The per cent binding (equilibrium dialysis) was higher for women (94.9 +/- 0.3) than for men (93.0 +/- 0.2). Paper electrophoresis showed that significant fractions of 3H-delta5-diol migrated with both the beta-globulin and albumin fractions. Estrogen administration to two normal men increased the per cent binding of delta5-diol to plasma proteins and decreased the metabolic clearance rate towards the values found for normal women.

Seasonal changes in blood plasma protein fractions in chinchilla females and males were found. Plasma albumin levels in both sexes vary according to season, generally low in winter and spring and high in summer and autumn. The levels of alpha 1-globulin and gamma-globulin increase markedly in spring (1.5 times higher than in winter and autumn). In chinchilla females, the levels of alpha 2-globulin and beta 2-globulin varied biphasically, being higher in winter and summer. In males, clear seasonal trends in the levels of both fractions were not observed. The beta 1-globulin fraction levels vary throughout the year. In females as well as males, globulin decreases during winter to minimal values in late spring, and then increases again during the summer to remain at the same level till autumn.

Alterations in the carbohydrate composition of serum protein fractions have been determined in pooled sera from 35 children with protein-calorie malnutrition (PCM), 30 children treated for PCM, and 24 age- and social status-matched controls. Total protein-bound hexose (PBH), protein-bound sialic acid (PBSA), and protein-bound fucose (PBF) were elevated in PCM, but only PBF returned to control levels with treatment. Ratios of bound carbohydrate to protein in the unfractioned serum were elevated in PCM but PBH and PBF protein or globulin ratios returned to normal with treatment. The most marked change in carbohydrate composition occurred in the alpha1-globulin fraction. Molar ratios in the individual globulin fractions indicated an increase in carbohydrate moieties as follows: PBSA greater than PBH greater than PBF.

Using polyacrylamide gel electrophoresis and radioiodinated plasma proteins, data on the rate constant for synthesis and fractional degradation rates for albumin, alpha1-, alpha2-, beta-, and gamma-globulins were obtained during accelerated amyloid induction in a murine model. The results indicate that during amyloid induction there is an increased rate of synthesis of alpha2-, beta-, and gamma-globulins but only the alpha2-globulin degradation rate is accelerated. In this experimental system, should amyloid protein be a degradation product of a plasma fraction, the alpha2-globulin appears as the most likely precursor. The implications of our findings are discussed, and a new general mechanism of amyloid production is proposed.

1. Colloid osmotic pressure, plasma osmolality and plasma protein concentration, percentage composition and A/G ratio were measured before and after haemorrhage in the pigeon. 2. Colloid osmotic pressure, total protein, albumin and beta-globulin concentrations decreased significantly immediately post-haemorrhage, but were significantly elevated after one week. 3. Osmolality and A/G ratio values were significantly increased post-haemorrhage. 4. The results are discussed in relation to fluid exchange across capillaries.

The origin and course of enzootic white muscle disease affecting young cattle in spring months after transfer from stables to pastures were accompanied by an apparent tendency to dysproteinemia. Clinically diseased animals showed a decrease of total protein in the blood serum and considerable changes in the protein spectrum. In comparison with findings in the set of clinically healthy controls, the animals affected by the white muscle disease showed a depression of albumins and a simultaneous increase of alpha- and beta-globulins and a decrease of gamma-globulins.

Circadian rhythms of blood total proteins, albumin, alpha 1-, alpha 2-, beta- and gamma-globulins were documented in 80 Wistar SPF adult male rats, synchronized by natural light (06.00-18.00 h) and darkness (18.00-06.00 h) during the month of October 78. Blood was sampled at four fixed time points in the 24 h scale (i.e. 04.00, 10.00, 16.00 or 24.00 h). Total proteins, albumin, alpha 2- and gamma-globulins showed a statistically significant rhythm with a maximum at 04.00 h. The data obtained in anaesthetized rats under artificial synchronization and in man are compared, taking into account that the rat is a nocturnally active rodent. The present work partially confirms the hypotheses of previous chronopharmacological studies, thus e.g. curarizing substances have a mimimum activity when the protein plasma level, especially albumin, is the highest.

Prolonged lysine deficiency resulted in inhibition of growth of the rat and in lowered levels of albumin and beta-globulins, but not of total liver proteins. The apparent incorporation of [3H]lysine into total and chromosomal liver proteins, however, was increased in lysine deficient rats relative to pair-fed controls. The concentration of free lysine in neither serum nor liver was altered in lysine deficient rats. The specific radioactivity of liver free lysine 2 hours after administration of [3H]lysine was noticeably elevated in the deficient rats. However, when the pool of liver free lysine is considered, synthesis of all proteins studied was inhibited. The largest inhibitory effect was seen in serum albumin and total liver protein synthesis. Inhibition of snythesis of nuclear chromatin protein was less pronounced. The data indicate an adaptive mechanism operates to preserve liver lysine in rats fed lysine deficient diets for a prolonged period. In spite of retention of lysine, the synthesis of liver and serum proteins was inhibited.

The changes in the levels of total protein and four globulin fractions were followed up throughout the entire course of complications caused by Gram-negative facultative pathogens in 37 acute cases of respiratory insufficiency accompanying different underlying illnesses and in 9 chronic, bedridden patients given artificial ventilation. At the onset of the infectious complications, in the first place in septic shock, the levels of various globulin fractions showed a decrease corresponding to a half-life of 2 to 4 days. Neither the increased catabolism, nor the protein losses by the urine and tracheal secretions offer a sufficient explanation for the escape of globulins of this extent from the plasma. It seems that this is a consequence of the increase in capillary permeability due to the effect of antigen-antibody reactions and that of endotoxin. As a result, in the critical phase of the infectious complications, at the point of culmination, e.g. in septic shock, diminished amount of different globulins is transported to the site of utilization, that is, to the inflammatory area.

This paper deals with the behaviour of serum protein fractions in rats fed 22 resp. 52 weeks a 50% or 3% fat diet using Millipore electrophoresis. The total serum protein concentration was also estimated. In rats on the high-fat diet the albumin fraction significantly dropped, while elevated levels of alpha 1- and gamma-globulin fraction were found. Serum protein content was slightly elevated in rats fed the diet 22 weeks, but this elevation was only significant after 52 weeks feeding. Within the same diet group there were no significant differences observed.

The binding of tritium-labelled tubocurarine to separate protein fractions of sera from normal subjects and patients with hepatic disease was measured by an electrophoretic technique. The binding of the drug to gamma globulin and albumin solutions also was studied using equilibrium dialysis. The major portion of the drug, 82-90%, was bound to the gamma globulin electrophoretic fraction of both normal and patient sera. However, as measured by equilibrium dialysis, only 15.8% of the drug was bound to the gamma globulin and 23.8% to albumin. Equilibrium dialysis yields the data by which the validity of other methods for measuring drug-protein binding can be judged. Since in a previous study we also found no difference in binding of the drug between healthy individuals and patients with hepatic disease, equilibrium dialysis measurements may reflect better the binding of the drug in vivo.

The influence of long term plasmapheresis on the health of donors was examined in two groups of plasma donors that donated mean volume of 411 ml of plasma during 176 weeks and 670 ml of plasma during 123 weeks (p less than 0,05). The control group consisted of 27 whole blood donors. Statistically no significant differences (p greater than 0,05) were found in the concentrations of total proteins, albumin, gammaglobulins, immunoglobulins, alpha 1 antitrypsin, alpha 2 macroglobulin, plasminogen, fibrinogen, factor V, factor VIII, GPT and alkaline phosphatase. Although the difference was significant for bilirubin and GOT the mean values were within the normal range. Significant elevations were found in alpha 1 globulins, and alpha 2 globulins in the group that donated 411 ml of plasma/week after 35 sessions. In this latter group of donors the elevation of beta globulins was observed after 100 sessions. On the basis of these results we suggest that plasma donors should not donate more than 500 ml of plasma per week and that the maximal number of regular plasmapheresis should not exceed 70. The yearly number of sessions should therefore not exceed 50 and the yearly donated volume of plasma should be not more than 25 liters.

Six representative clinical isolates of Serratia marcescens were examined for proteolytic activity against various proteins of normal fresh human serum. The extent of proteolytic activity was screened with micro-scale immunoelectrophoresis and quantitatively documented with the aid of Laurell's rocket electroimmuno assay. The 6 S. marcescens strains regularly altered, albeit to varying degrees, complement components C3a, C3c, C4, C5, and C9, and haptoglobin. Apolipoprotein and immunoglobulin A, the latter derived from human colostrum, were attacked by 5 and 4 isolates, respectively. Two isolates altered alpha 1-antitrypsin, whereas only one isolate interacted with alpha 2-macroglobulin and transferrin. In contrast, alpha 2-HS-glycoprotein, alpha 1-antichymotrypsin, and serum IgA, IgG, and IgM immunoglobulins were not affected by the test strains.

The effect of ochratoxin alone and in combination with aflatoxin and Brucella abortus antigen on complement activity, serum proteins, and antibody response in guinea pigs was investigated. Ochratoxin did not affect complement activity or antibody response and there was no interaction between ochratoxin and aflatoxin on any of the responses tested. Ochratoxin significantly lowered the level of beta-globulin in serum of guinea pigs. There was no significant interaction between aflatoxin and antigen on lowering of the serum albumin levels of guinea pigs.

Rats underwent surgical removal of either the proximal or distal half of the small bowel. 5-6 weeks later, total protein concentrations and electrophoretic patterns were determined in sera from the two groups of resected animals. The data compared to similar measurements from sham-operated and unoperated control groups, showed no differences between resected or control animals. This indicates re-establishment of overall nutritional adequacy by this time interval after substantial loss of either proximal or distal small intestine.

As a crucial step towards understanding the mechanism of localisation of radiopharmaceuticals in specific target organs, the interaction of the radiopharmaceuticals 99mTc-DMS and 99Tc-DMS with blood serum proteins was studied. The interaction of 99mTc-DMS radiopharmaceutical was examined from two aspects: total protein binding as well as specificity of binding to certain classes of proteins. After in vitro labelling of human sera with 99mTc-DMS, the following values of bound radioactivity to total serum proteins were determined: 65% +/- 3.2% by gel-filtration chromatography; 72% +/- 4.6% by dialysis; while on the basis of precipitation by perchloric and trichloroacetic acid 72.7% +/- 6.8% and 71% +/- 2.3%, respectively. Distribution of 99mTc-DMS or 99Tc-DMS among serum proteins was analysed by agarose gel electrophoresis of the sera at pH 8.6 after in vivo and in vitro labelling of human sera with 99m-Tc-DMS, while the same analysis was performed with 99Tc-DMS complex after in vitro labelling of human and rat sera as well as after in vivo application to the rats. The results obtained demonstrate that carrier serum proteins investigated by agarose gel electrophoresis were in the migration zone of alpha 2-, alpha 1- and beta 1-globulins, whereas the radioactivity found in the serum albumin zone was negligible. Interaction of both Tc-DMS complexes with proteins was very similar, and this conclusion was in good correlation with our previously obtained results in investigations concerning the biochemical behaviour of these complexes.

An evaluation of serum protein and immunoglobulins with regard to valproic acid (VPA) and phenytoin (phen) serum levels was performed in 28 epileptic patients. Serum antiepileptic levels were measured in fasting conditions. All patients were classified into the following groups: A (VPA below 50 micrograms/ml), B (VPA 50-89 micrograms/ml), C (VPA above 89 micrograms/ml), D (VPA 50-89 micrograms/ml and phen below 10 micrograms/ml). Patients of group C showed higher serum protein values than groups A (P less than 0.02), B and D (P less than 0.001). The alpha 2 and beta-globulin fractions were higher in group C than the remaining groups (P less than 0.05). Immunoglobulin A, G and M remained unaltered in all patients.

The effect of Fenchlorphos on postirradiation changes of serum protein levels and nucleic acid content in rat liver were investigated. It was found that this compound significantly decreases postirradiation changes in serum proteins, properdin level and nucleic acid content in rat liver. An important role of these phenomena in radioprotective action of Fenchlorphos is suggested.

The calves of the Red Spotted breed and their first-calver mothers were subject to the study of total proteinemia and of the changes in protein fractions before parturition and in a ten-day period of post-partal development. The relations between these parameters were also studied. Calves up to the 10th day of life show a rise in total proteinemia whereas cows show insignificant changes. The level of albumins in calves exhibits a slight fluctuation, whereas in mothers it increased before parturition, followed by a drop which lasted until the end of the test period. alpha-globulins show a decreasing tendency in calves from the fourth day of age and have higher values than in cows. beta-globulins in cow blood serum before parturition increase. The level of gamma-globulins in calves rises until the end of the first week of life. A linear correlation dependence was found between the values of beta-globulins in cows and calves in the first two post-partal days and between the value of beta-globulin level of mothers prior to parturition and of calves at birth. In gamma-globulins the correlation dependence is always significant, starting the first day after birth.

Serum protein of Swiss albino mice infected with Ancylostoma caninum larvae, were analysed electrophoretically. Twenty mice were infected with a dose of 1000 larvae and the alterations in serum protein during an infection period of 30 days were recorded and compared with uninfected controls. The result showed a significant decrease in albumin and gamma globulin with an increase in beta globulin. There were no significant changes in the alpha-1 and alpha-2 globulins. The total globulins increased and A/G ratio decreased. These changes appeared to be remarkable on the 9th day after infection.

The serum proteins and their fractions were analyzed in the Moroccan "Timahdite" sheep. The values of those parameters in 20 two year-old adult animals were: total proteins 64.2 +/- 1.6 g/l; albumin 458 +/- 31 mumol/l; alpha-glob 11.9 +/- 1.0 g/l; beta-glob 6.2 +/- 1.6 g/l; gamma-glob 14.7 +/- 2.3 g/l. The total proteins increase with age is particularly due to an increase of the globulin fractions. In animals with liver or pulmonary affections the total proteins are increased. The amount of albumin is lower in liver diseases, whereas the globulin fractions are increased in both pathological processes.

1. 125I-labelled beta 2-microglobulin (beta 2m) was injected into rats and protein or non protein-bound radioactivity was determined in plasma urine and several organs. 2. The observed kinetics differed from those expected according to the bicompartmental model for plasma protein turnover. The difference was attributed to the binding of a part of the tracer to a plasma component. Chromatography of plasma taken after injection of beta 2m showed an additional peak of radioactivity at the 55,000-80,000 daltons position. 3. In animals with ligated renal arteries, disappearance of the tracer from the plasma was markedly prolonged, and little non-protein-bound radioactivity was detectable in plasma, indicating that the kidney was the major site of catabolism of beta 2m. 4. Chromatography of plasma from control rats and rats with ligated renal arteries showed that the kidney was the major site of catabolism for free beta 2m only. 5. In normal rats, the urine was found to contain only non-protein-bound radioactivity.