The Relationship Between Weight Gain and Free Amino Acid Concentration of Plasma and Liver in Rats Fed a Diet Supplemented With Various Amounts of Lysine

Abstract

This study was conducted to determine the effect of feeding graded levels of dietary lysine on weight gain and free amino acid concentra tions in blood plasma and liver of weanling rats. Animals were fed on diets containing 11.6% wheat gluten (equivalent in nitrogen to a 10% casein diet) supplemented with graded levels of L-lysine HCl (0 to 10%) for 14 days. An outline of the results obtained follows: 1) Maximum weight gain was observed with the groups fed the lysine supplement in the 0.64 to 1.8% range. Growth declined with further in crease of dietary lysine.2) Blood and liver were sampled after decapitation 6 hr after the fi nal feeding on the 14th day, and amino acid concentrations were determined. Plasma lysine concentrations rose rapidly as dietary lysine increased and reached the maximum level with the 1.8% lysine supplementation. With the large supplement diet, the lysine con centrations maintained a plateau. Plasma threonine levels were high when dietary lysine was low.3) Similar responses of lysine and threonine concentrations in liver to the increase of dietary lysine was also observed, but the effect was markedly less than those of plasma. Most other amino acids in plasma and liver were nearly unchanged even when the dietary lysine was varied over a wide range.Extensive studies (1-3) have been made on the relationship between weight gain and the concentration of free lysine in the blood plasma of animals fed 277

Supplemental Effect of Lysine on Growth Depression of Rats Fed Wheat Gluten Diets Containing Excessive Amount of Some Individual Amino Acids

“…Furthermore, the supplement of lysine to the excess arginine diet tended to result in increases of arginine and lysine levels in plasma. The decline of plasma threonine concentration in animals fed diets supplemented with lysine was consistent with the results of previous observa tions (6,8 Table 2. Liver arginase activities in rats fed the basal (11.6% wheat gluten), basal plus 0.6% lysine• HCI, basal plus 5.0% arginine• HCI, and basal plus 5.0% arginine• HCl plus 0.6% lysine• HCl diets, respectively.…”

“…Vitamin A (2,000 IU) and D2 (200 IU) were also added.4 Additions of 5.0% of single L-arginine• HCI, L-tryptophan, L-phenylalanine, L-methionine and L-tyrosine, with or without 0.6% of L-lysine• HCL were made at the expense of a-starch. This supplemental level of lysine to the basal diet was adequate for the requirement of lysine (6). When the experimental diet containing 5.0 arginine• HCl was prepared, 2.0% of sodium bicarbonate was included at the replacement of cellulose powder.…”

Threonine Requirement for Reproduction in Swine

“…Conversely, a relationship between increasing dietary lysine and plasma threonine levels has been observed. An inverse relationship between dietary lysine level and plasma threonine has been reported by Muramatsu et al (1973) and Woerman and Speer (1976). Yamashita et al (1967) found that elevated levels of dietary lysine in creased liver threonine dehydratase activity.…”

The lysine requirement for reproduction in swine

“…In both the fasting and postfeeding plasma samples, ment is beginning to be met (Muramatsu et al, 1973)• The lysine^threonine ratio approached and surpassed unity be tween 0.30 and 0.4l^ lysine in this experiment (Table 1). …”

“…Morrison et al (1961) Muramatsu et al (1973) found that plasma lysine increased well before the point of maximum grovrth with rats. Mitchell et al (1968), Stockland et al (1970) and Lewis and Speer (1974) determined that the plasma amino acid response involved two linear mathematical functions, when the data ware plotted on a graph, the intercept of the two functions was found to be very close to the amino acid requirement of the animal.…”