Rat Plasma Albumin Research Articles

Lipid monolayers: interactions with the apoprotein of high density plasma lipoprotein

Monolayer techniques were used to study the interactions of various lipids (cholesterol, lysophosphatidyl choline, phosphatidal ethanolamine, phosphatidyl choline, sphingomyelin, stearic acid, and lipids extracted from plasma high density lipoproteins and very low density lipoprotein) with the lipid-free protein subunit of rat plasma high density lipoprotein and with rat plasma albumin. The proteins were injected under the lipid monolayer at fixed area, and the increase in surface pressure (decrease in surface tension) was measured as a function of time. With all lipids, both the rate and magnitude of this increase were greater with the apolipoprotein than with albumin. The degree of film penetration of pure lipid films (at an initial film pressure of 15 dynes/cm) by the two proteins followed the same order: cholesterol > phosphatidal ethanolamine > phosphatidyl choline > stearic acid > sphingomyelin > lysophosphatidyl choline. Other variables studied were protein concentration, initial film pressure, and pH. Two distinctive properties of the apolipoprotein were the penetration of lipid films at pressures above the collapse pressure of the protein, and the formation of a film even at low salt concentration. High surface activity and strong interaction of HDL-protein with lipid monolayers may be associated with the flexibility of the protein molecule due to absence of disulfide bridges. The unusual surface activity of HDL-protein may be intimately related to the mechanism of formation of the lipoprotein.

Post-albumin, a foetal-specific rat plasma protein: Purification, physicochemical and immunological studies

1. The foetal-specific post-albumin of rat plasma was purified by electrophoresis on a Pevicon block. 2. The sedimentation coefficient, diffusion coefficient and molecular weight were determined for this protein and found to be similar to those of adult rat plasma albumin. 3. Foetal post-albumin and adult albumin were compared immunologically and shown, with rabbit antisera, to share no antigenic determinants, suggesting different genetic control of the production of each. 4. It is suggested that the disappearance of post-albumin in the newborn animal may result from the disappearance of haemopoietic tissue from the rat liver with advancing age.

Sites of plasma albumin catabolism in the rat.

The effects of splenectomy, partial and complete gastrectomy, partial and subtotal hepatectomy, and evisceration on the catabolism of I131-labeled screened and unscreened plasma albumin in rats was studied. Splenectomy and removal of jejunum and ileum had no effect, but complete enterectomy, hepatectomy, and evisceration depressed plasma albumin breakdown as compared to sham-operated controls. Plasma albumin breakdown was found to proceed at an appreciable rate in eviscerated rats, and it appears that up to half of albumin breakdown in the rat occurs in nonvisceral sites. In perfused rat liver unscreened iodoalbumin is rapidly degraded, but the breakdown of screened albumin is low, accounting for about 15% of total plasma albumin catabolism in vivo.