Extravascular Albumin Mass and Exchange in Rat Tissues

Abstract

1. Extravascular albumin in carcass, skin and gut of rats was extracted and the albumin content estimated by several methods. Assay by electrophoresis on acrylamide gel, by immunodiffusion and by radioimmunoassay were in essential agreement. The method used previously, precipitation with antibody followed by alcoholTeA extraction, underestimates the amount of albumin in tissue extracts, because extraction from the antibody precipitate is not complete. This method is valid, however, for specific activity determination.2. Normal rats contain from 500 to 650 mg of albumin per 100 g body weight. Of this, 20-25% is in the circulation, 3~0% in the carcass (mainly but not exclusively muscle), 20-25% in skin and 10% in gut.3. The extracellular water of muscle, carcass, skin and gut was estimated from the distribution of mannitol and sulphate. With the exception of gut, both methods agreed closely. Extracellular, extravascular water constitutes about 23% of the body weight of 150-200 g rats. The extracellular water in muscle is about 20% and in skin, 40%. In gut the extracellular water cannot be estimated reliably by these compounds.4. Muscle contains about 3·5 mg/g of extravascular albumin; skin and gut, 7-8 mg/g. The concentration ofextravascular albumin in extracellular water of muscle and skin is 16-20 mg/ml, or 50-60% of the concentration in plasma. In the small intestine the concentration of albumin is higher, possibly similar to that in plasma.5. In rats with severe aminonucleoside nephrosis, body albumin was depleted to 100-200 mg/IOOg. Of this, 15-25% was in plasma, 50% in carcass, and about 15% in skin. Ascitic fluid contained only a few mg of albumin.6. The specific activity of extravascular albumin of tissues was followed after intravascular injection of 125 1_ or 1311-labelled albumin. The specific activity of carcass albumin increases rapidly, becoming equal to that in plasma after less than

Whole-body albumin mass and distribution in rats fed on low-protein diets

“…Values for circulating albumin mass given by Katz et al (1970) Despite the fact that the same extraction procedures were used, and allowing for the small contribution of albumin from the viscera to total extravascular albumin mass, the amounts of extravascular albumin found in the present experiments were substantially lower than those reported by Katz et al (1970) of 3-64-5*10g/kg. This difference, combined with the likely difference in plasma volumes, explains the wide divergence of mean values for the ratio, extravascular: vascular albumin mass which were never less than 3-7 in the experiments of Katz et al (1970) and not greater than 1.6 in the work reported here; Freeman & Gordon (1964) found a ratio of 1.8 in normal hooded rats.…”

“…This difference, combined with the likely difference in plasma volumes, explains the wide divergence of mean values for the ratio, extravascular: vascular albumin mass which were never less than 3-7 in the experiments of Katz et al (1970) and not greater than 1.6 in the work reported here; Freeman & Gordon (1964) found a ratio of 1.8 in normal hooded rats. In other experiments in this laboratory attempts have been made to increase the yields of extravascular albumin using other extraction procedures, but this has never been possible and it is difficult, therefore, to explain the differences between the present work and the only comparable published work without recourse to the assumption that values differ between strains of rats.…”

“…More blood was then removed and to deplete the tissues of residual blood still further, 5-10 ml saline (9 g NaCl/I) was injected into the heart and the fluid re-aspirated. The animals were then eviscerated, the entire skin and carcass minced and 10--20 g portions extracted as described by Katz et al (1970) using a Silverson homogenizer with a slotted disintegrating head (Silverson Machines Ltd, Chesham, Surrey). Viscera were extracted directly without prior mincing.…”

Changes in plasma volume and protein content during exposures of working men to various temperatures before and after acclimitization to heat: separation of the roles of cutaneous and skeletal muscle circulation

“…More likely is the involvement of a vascular bed wherein blood flow is increased and where the capillaries are more permeable to plasma proteins than are cutaneous capillaries. The work of Katz, Bonorris, Golden & Sellers (1970) and indicate that this circulatory bed is contained within skeletal muscle. However, evidence also exists suggesting that blood flow in the gastrointestinal tract may shift from one capillary bed to another without changing the volume of splanchnic flow (Kampp & Lundgren, 1968).…”

Quantitative Significance of Plasma Albumin Metabolism in the Whole Body Protein Turnover in Rats

“…100 were added to the reaction mixture up to a final concentration of 0.5 and 1.0%, respectively, as has been reported in several publications. tO -15 ) The method to determine the plasma albumin mass in the whole body was essentially the same as that of Katz et al 16 ) After having taken blood for plasma volume estimation, the rats were frozen with dry ice and minced in a meat chopper. The minced rats were homogenized further by a Waring blendor with 500 ml of ice-cold sodium deoxycholate solution (0.05% in 0.9% NaCI, pH 8.0).…”