Plasma Protein Production as Influenced by Parenteral Protein Digests, Very High Protein Feeding, and Red Blood Cell Catabolism

When blood plasma proteins are depleted by bleeding, with return of the washed red cells (plasmapheresis), it is possible to bring dogs to a steady state of hypoproteinemia and a constant level of plasma protein production if the diet nitrogen is controlled and limited. Such dogs are outwardly normal but have a lowered resistance to infection and to certain intoxications. Certain protein digests given by vein may favor good production of plasma protein, as well as nitrogen and weight equilibrium, over long periods in these standardized dogs. These digests may be equally effective when given subcutaneously or intraperitoneally and more effective orally (one dog). Certain other digests may not be well utilized. The total nitrogen of the protein digests is better retained upon oral feeding than parenteral injection. Most of the excess nitrogen excretion is not in the urea and ammonia fraction of the urine. The rate of plasma protein production may reach as high as 1 gm./kilo/day in the dog when ample protein of good quality is fed. The products of catabolism of red blood cells in vivo may add to the production of plasma protein, at least during the administration of casein digest by vein.