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 uniform plasma protein production on a basal low protein diet. These dogs are clinically normal with normal appetite, no anemia and normal nitrogen metabolism. These dogs become test subjects by which various factors relating to plasma protein production may be tested.
The normal dog (10 to 13 kg.) has a substantial reserve store of plasma protein building material (10 to 60+ gm.) which requires 2 to 6 weeks plasmapheresis for its complete removal. After this period the dog will produce uniform amounts of plasma protein each week on a fixed basal diet.
Dogs previously depleted by plasmapheresis and then permitted to return to normal during a long rest period of many weeks, may show much higher reserve stores of protein building material in subsequent periods of plasma depletion (see Table 1).
Under uniform conditions of low protein diet intake when plasmapheresis is discontinued for 2 weeks the plasma protein building material is stored quantitatively in the body and can subsequently be recovered (Table 4) in the next 2 to 3 weeks of plasmapheresis.
Given complete depletion of plasma protein building reserve stores the dog can produce very little (2± gm. per week) plasma protein on a protein-free diet. This may be related to the wear and tear of body protein and conservation of these split products.
Abscesses produced in a depleted dog during a fast may cause some excess production of plasma protein which is probably related to products of tissue destruction conserved for protein anabolism.
Gelatin alone added to the basal diet causes very little plasma protein production but when supplemented by tryptophane gives a large protein output, while tryptophane alone is inert.