Serum Albumin Changes in Hypoproteinemic Dogs Following Administration of Methionine or Phenylalanine

The observation by Whipple and his coworkers that single amino acids and pure chemical substances increase the production of hemoglobin 1 and serum protein 2 raises the question of whether observed increases in serum protein after protein feeding are not solely the result of chemical stimulation, or mobilization from body stores of protein, as distinguished from a new synthesis from the ingested protein materials. If so, recorded differences in proteins (when concluded from changes in serum protein levels) would be merely an expression of a difference in amino acid composition and not necessarily express the nutritive value of the proteins for growth or maintenance.

Before such an interpretation can be made, it is essential to have additional data; and especially to determine whether single amino acids under conditions of low dietary protein, as in the procedure of Weech and Goettsch 3 will effect an increase in serum protein.

Fourteen dogs were used for the study and the above procedure 3 followed in all details. Total protein, albumin and non-protein nitrogen were run on the plasma from blood taken at the beginning and end of 3-week depletion on the low protein diet, and after one week regeneration. A few observations were made after 2 weeks' regeneration. Supplement consisted of 1 g dl-methionine∗ or 1 g dl-phenylalanine∗ added daily to the 53 g per kilo of the basal diet. Table I gives the summarized findings.

The 7 dogs fed 1 g methionine showed an average increase in serum albumin of 0.157 g %. If the Weech and Goettsch figure of 0.15 (to compensate for the fall in albumin that would have been observed during the 4th week if the supplement had not been fed) is added, the potency value of methionine becomes 0.307 ± 0.028.