The Conjugated, Non-Protein, Amino Acids of Plasma. Iv. A Difference in the Utilization of the Peptides of Hydrolysates of Fibrin and Casein

Abstract

Peptides are utilized much less readily than free amino acids upon the intravenous infusion of a partial enzymatic hydrolysate of casein (Amigen), as indicated by the greater accumulation and longer persistence of peptides in plasma, and their loss to the extent of 36 to 53 per cent into the urine (1). However, a partial acid hydrolysate of fibrin twice as rich in peptides as Amigen (containing about % of its amino acids in a conjugated state) has been found to have a high biological value upon intravenous administration to dogs, as compared with fibrin given orally (2). These observations suggest a possibility of considerable interest to the subject of peptide metabolism, namely, that the peptides derived from fibrin may be more efficiently utilized than those of the casein hydrolysate. This we have found to be the case.Five per cent solutions of the fibrin hydrolysate in 5 per cent glucose were infused intravenously into convalescent male patients and into a normal subject, in 3 different quantities-1,000 ml., 878 ml., and 485 ml.,-the latter 2 quantities supplying according to our analysis the same quantity of total a-amino nitrogen and bound a-amino nitrogen respectively, as a liter of 5 per cent Amigen. (The fibrin hydrolysate was not only much richer in peptides because of the limited hydrolysis, but also somewhat richer in total amino acids.).With the 2 larger portions, containing 2 to 2.3 times the quantity of peptides supplied by a liter of Amigen, dialyzable amino acid conjugates (peptides 1) reached concentrations in plasma somewhat higher than for Amigen at similar infusion rates (Table I). However, when the quantities of peptides infused were alike, the plasma levels were lower with the fibrin hydrolysate. The highest 1 term peptides will be used here for the dialyzable amino acid conjugates, although other nonprotein conjugates besides peptides may be included. level of peptide a-amino nitrogen yet observed, 6.3 mgm. per cent, was not associated with discomfort. The infusion of either hydrolysate brought the free a-amino acid nitrogen of plasma to levels lower than were observed before the infusions. The curves picturing the removal of the conjugates from plasma show the same aspects with the 2 hydrolysates (Figure 1). Without regard to the rate or quantity of the infusion, the loss of peptides into the urine was less for the fibrin hydrolysate, 26 to 28 per cent of the peptides infused (Table II). For infusion times of 1.5 to 4 hours, losses of 40 to 53 per cent were characteristic for the peptides of 1 liter of 5 per cent Amigen. In the 2 cases where the conditions were most similar (experiment 52, reported previously [1], and experiment 14), the same quantity of peptides being infused into the same normal subject in very nearly the same time interval, the loss of peptides was 27 per cent for the fibrin hydrolysate and 53 per cent for the Amigen. The losses of free aamino acids were larger during infusion of the fibrin hydrolysate than when Amigen was injected. Undoubtedly a part of the free amin...

Effects of Simultaneous or Prior Infusion of Sugars on the Fate of Infused Protein Hydrolysates 12

“…Our first thought was that the larger diuresis usually obtained with the glucose-containing hydrolysate might account for this finding; in agreement with others we have found much higher glucose levels in the blood during the infusions than for fructose, and much larger losses of glucose into the urine. Therefore, comparable degrees (8).…”

The Effects of the Rate of Administration of Amino Acid Preparations on Urinary Wastage of Amino Acid Nitrogen in Man

“…Increased urinary loss of "bound" amino acid nitrogen has also been found to occur in dogs after the intravenous administration of Amigen by Cox and Mueller (7). Recently, Christensen and associates (8) increase the rate of urinary loss of amino acid nitrogen. The work presented here, using human subjects and a rapid administration of amino acids (Preparation V), is in agreement with their report.…”

“…Earlier investigators (2,3,4) found that if amino acid preparations were given intravenously at a slow rate, usually less than 8 per cent of the administered amino acid nitrogen was lost by urinary spillage. Thus, it was desirous to learn whether the advantages gained by the rapid intravenous infusion of the well-tolerated amino acid mixtures might be offset by an increased urinary loss.…”

The Conjugated, Non-Protein, Amino Acids of Plasma. V. A Study of the Clinical Significance of Peptidemia

“…On the other hand whenever the plasma peptide nitrogen is elevated by a few mgm. per cent by the intravenous injection of peptides (in the form of incomplete hydrolysates of protein) there is a massive peptiduria (27,28). A dissimilarity is apparent in the nature of the "peptides" of plasma in the two situations.…”