Hereditary phosphofructokinase (PFK) deficiency was diagnosed in two Wachtelhund dogs and suspected in three related Wachtelhund dogs with exercise intolerance, hemolytic anemia, and pigmenturia. Severe, persistent reticulocytosis in light of only mild anemia together with hemoglobinuria after strenuous exercise suggested PFK deficiency. Low erythrocyte PFK activity together with low 2,3-diphosphoglycerate concentrations and a high hemoglobin-oxygen affinity confirmed the diagnosis. The PFK deficiency is due to a single missense mutation in the muscle-type PFK M-PFK gene in English springer and American cocker spaniels, whippets, and mixed-breed dogs; however, these PFK-deficient Wachtelhunds do not have the same PFK mutation.
The gist of this paper is that certain casein digests given by vein or subcutaneously are promptly used by the hypoproteinemic dog to produce needed plasma proteins. The digest of casein is approximately as effective by vein as is the casein digest or whole liver equivalents given by mouth. The digests tested are essentially non-toxic as used.A considerable series of experiments on dogs done in this laboratory has been reported during the past several years (9,15,4,11) to show that normal dog plasma given by vein to the protein fasting dog can supply all protein requirements. The dog has been kept many weeks in health, weight balance, and positive nitrogen equilibrium by suitable amounts of plasma by vein and sugar, fat, minerals, and accessories by mouth.Normal dog plasma protein given by vein during such protein fasts is utilized much more effectively than protein by mouth. It is evident from these previous experiments, and others of Howland and Hawkins (10), that the plasma proteins are utilized in the body more directly, with less waste and with but slight cleavage into large aggregates when needed to supply the protein requirements of the fasting dog. This exchange of proteins between the blood plasma and body cells has been discussed in recent papers (13,14). Table 5 (period 17) also shows how effectively plasma protein is used in the fasting dog as compared with the casein digest. Note the low urinary nitrogen when plasma protein is given by vein-about one-half the amount recorded when equivalent amounts of casein digest are given by vein. However, the casein digest by vein is as effective in plasma protein formation as liver protein or casein digest given by mouth. This would support the current belief that practically all food proteins are reduced to amino acids and peptides before utilization for protein building in the normal body.In the experiments tabulated below we assume that hypoproteinemia offers a strong continued stimulus to plasma protein regeneration. Daily
Given healthy dogs, fed abundant iron and a limited protein diet, with sustained anemia due to simple bleeding, we can study the capacity of each animal to produce new hemoglobin and plasma protein. Some dogs can produce much hemoglobin and enough new plasma protein to maintain the plasma protein concentration at approximately a low normal level. It is probable that their plasma protein producing capacity is not fully extended (Table 2). Other dogs (Table 5) can produce the same amount of hemoglobin but a hypoproteinemia develops and continues which should mean a maximal stimulus to produce new plasma protein. In such dogs we have strong stimuli to produce simultaneously new hemoglobin and new plasma protein. The ratio of plasma protein to hemoglobin varies from 40 to 60 per cent. The total new formed blood protein may amount to 30 to 40 per cent of the total diet protein intake which shows that some dogs have remarkable capacity to conserve and use diet protein. In this emergency of simultaneous depletion of hemoglobin and plasma protein levels, the dog gives preference to hemoglobin manufacture no matter what one of the listed food proteins is tested.
When blood plasma proteins are depleted by bleeding with return of the washed red blood 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 but their resistance to infection is distinctly below normal. Introduction of variables into this standardized existence gives information relative to plasma protein production. Plasma protein production under these conditions with a plasma protein concentration of 3.5 to 4.2 gm. per cent is relatively constant. As the plasma protein concentration rises the plasma protein removed falls rapidly (Table 1). At 4.6 gm. per cent the protein removed is less than 50 per cent of the amount removed at a plasma protein level of 4.0 gm. per cent. Cystine appears to be an important amino acid for plasma protein formation. This shows in Table 2 and is supported by data coming from published experiments. These experiments related to the factors which control plasma protein production bear on the problems of shock, hemorrhage, and protein wastage and their treatment by plasma injections which hold the attention of surgeons and physiologists at the moment. Again we would emphasize the fluidity of body protein including plasma protein—an ebb and flow between protein depots and plasma protein—a "dynamic equilibrium" of body protein. A discussion of the passage of large protein molecules through cell borders is submitted.
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