[Resorption and incorporation of radioactive-labeled amino acids during administration of various protein carriers in rats. 3. Uptake of radioactivity by blood plasma, liver and muscular tissue and incorporation into tissue proteins after intragastric administration of 14C-leucine and 3H-glycine]

[Dynamics of amino acid and protein metabolism of laying hens after administration of 15N-labeled wheat protein. 5. Incorporation of 15N into the blood fraction and its amino acids]

12 colostomized laying hens which received 15N labelled wheat over 4 days were butchered 12 h, 36 h, 60 h and 108 h (3 animals each) after the last 15N application. The intake of 15N excess (15N') from the wheat amounted to 540 mg 15N' during the application period. The 15N' in the blood plasma decreased after the last 15N' application from 0.76 atom-% to 0.55 atom-% after 108 h, the labelling of the corpuscular components at the same measuring points increased from 0.28 to 0.50 atom-% 15N'. 96.6% of the plasma 15N' and 93.8% of that in the corpuscles is precipitable in trichloric acetic acid. The atom-% 15N' of histidine in the total blood remained unchanged in dependence on the butchering time. The 15N amount in lysine and arginine and that in the non-basic amino acids decreased inconsiderably in the period between 12 h and 108 h after the last 15N' wheat feeding.

[Protein digestibility and amino acid absorption in various segments of the digestive tract of pigs. 5. Results of the application of 35S-methionine]

The intake, excretion and the rate of flow of protein, methionine and 35S were measured at four pigs (live weight 63 kg) with re-entrant cannulae in the duodenum and the ileocecal region after the oral application of 35S-methionine and the feeding with a wheat + wheat gluten + lysine resp. a protein-free diet over a period of 7 days. From the measured values one pattern each for the N- and the methionine metabolism was laid down with the help of the compartment model, and the endogenous and exogenous levels of protein resp. methionine in the duodenum, the ileum and in feces were estimated.

[Secretion of radioactively labeled amino acids into the digestive tract. I. Report 14C labeling of the pancreas after subcutaneous injection of 14C-leucine in rats]

4 different groups of experimental animals (rats) were injected 14C leucine at 4 different levels of specific 14C activity. Groups A and B received a dosis of leucine corresponding to the daily leucine requirements of the animals. The specific 14C activity was high in group A and low in group B. Groups C and D were injected a leucine dosis at a level of 10% from the groups A and B. the specific 14C activity being again high (group C) or low (group D). The results showed that a true evalution of the experiment could lnly be achieved if the values were related to the true rate of labeling (DPM/mg N or specific 14C leucine activity). The "percentage of the injected dosis" proved to be unsuitable for the analysis of the experimental results when taken as reference frame. The levels of specific 14leucine activity in free plasma leucine were in the same order as the specific activities of the injected solutions (C greater than A greater than D greater than B) whereas the order of specific 14C leucine activities in the TCE-soluble fraction of the pancreatic gland (TCE-trichloroacetic acid) was found to be A greater than C greater than B greater than D. This was due to the higher rate of 14C-leucine transfer into the protein fraction in the animals of group C and D receiving a normal supply of leucine. In these groups an equilibrium in specific 14C-leucine activity between the TCE-soluble and TCE-precipitable fractions was achieved 20-30 mins after injection. A relatively high degree of labelling of the pancreatic protein was noted as early as about 2 minutes after the injection of 14C-leucine. This indicates that in studies on amino acid absorption the secretion of those amino acids that are first absorbed and then resecreted via the pancreatic gland should always be taken into account.

[Nitrogen metabolism of broilers fed 15-N labeled wheat. 4. 15-N concentration in muscles and nitrogen utilization]

Broilers were fed 15N labelled wheat and the concentration of the labelled isotope in muscular tissue was determined. A negative correlation was found to exist between the percentage proportion of N in the muscle fractions and the level of 15N frequency established 12 hrs after administration of the labelled ration. Higher rates of tracer incorporation were observed in the muscles of legs and other muscles (predominatly red muscles) than in pectoral muscles (white muscles). The heart was shown to exhibit the lowest N content and the highest level of 15N frequency of all muscle fractions. In view of the fact that some specific difficulties will arise when certain factors (trace elements, vitamins, ergotropic substances, genetic factors) which influence the N metabolism of fattening poultry, are estimated on the basis of the conventional N balance trials the present tracer technique is recommended for use as an alternative method in studies of the kind just described. In the present trial 20% of the wheat N were utilized for the production of meat N in muscular tissue.

[Nitrogen metabolism of broilers fed N-15 labeled wheat. 3. Blood, liver, spleen, thymus, kidney, brain, pancreas, labile N reservoir]

Studies on the N metabolism of 4-week-old male broilers fed 15N Labelled wheat revealed a close correlation existing between the levels of 15N concentrations in the small intestine and in the plasma NPN fraction of the blood. The highest level of excess 15Natom0/0 in plasma proteins was noted as late as 20-30 hrs after administration of the last tracer dose. The mean life time of plasma proteins in broilers is less than 2.0 days. The rapid and statistically significant decrease of 15N frequency in the liver, spleen, thymus, and kidneys in the period from 12 hrs after withdrawal of the last 15N dose until the end of the trial reflects the intensity of N turnover in these organs. In the period from 6 hrs to 12 hrs after the last N intake the mean quantities of N in the liver, small intestine and kidneys decreased by 18%, 29%, 26% and 16%. The quantity of N accumulated in these organs after food intake is gradually released into the organism.