Showing papers on "Protein sparing published in 1991"

Whole-body and tissue protein synthesis during brief and prolonged fasting in the rat.

Abstract: 1 Little information is currently available on protein turnover during chronic protein loss situations We have thus measured the whole-body and tissue protein fractional synthesis rates (ks), the whole-body fractional protein degradation rate (kd), the capacity for protein synthesis (Cs) and the efficiency of protein synthesis (kRNA) in vivo in fed and fasted (1, 5 and about 9 days) 400 g rats 2 One day of starvation resulted in a reduced ks and an increased kd in the whole body ks was selectively depressed in skeletal muscles, mainly owing to a reduced kRNA, and was not modified in heart, liver and skin The contribution of skin to whole-body protein synthesis increased by 39% 3 During the phase of protein sparing (5 days of fasting), kd in the whole body decreased below the control fed level ks in skeletal muscles was sustained because kRNA was restored to 82-98% of the control value 4 Rats were in a protein-wasting phase after 9 days of starvation kd in the whole body did not increase and was actually 78% of the value observed in fed animals By contrast, ks in the whole body and tissues decreased to 14-34% of the control values, owing to reductions in both Cs and kRNA Whatever the duration of the fast, the contribution of the skin to whole-body protein synthesis largely exceeded that of skeletal muscle 5 The present findings suggest that the main goal in the treatment of chronic protein loss should be to sustain protein synthesis(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of monensin and a protonophore on protein degradation, peptide accumulation, and deamination by mixed ruminal microorganisms in vitro

Abstract: Mixed ruminal bacteria (80 mg N/liter) degraded casein and soluble soy protein rapidly (.68 and .72 mg N/[liter.min], respectively), but ammonia was produced at a slower rate (.08 and .10 mg N/[liter.min], respectively). Because there was little increase in cell protein, ammonia production could not account for all the degraded protein. Large quantities of non-ammonia, non-protein nitrogen (NAN-NPN) accumulated, and this NAN-NPN reacted more strongly (2- to 14-fold) with ninhydrin after it was treated with 6 N HCl (110 degrees C, 24 h) or pronase E. Even after 96 h of incubation, 10% of the protein N was still found in the NAN-NPN pool. Monensin had little effect on protein degradation, but it caused a large decrease in ammonia production (P less than .05) and an increase in NAN-NPN (P less than .05). These results indicated that significant quantities of peptide N could not be degraded by ruminal microorganisms and that monensin could increase peptide flow from the rumen. Because 3,3',4',5-tetrachlorosalicylanide, a protonophore that inhibits both Gram-positive and Gram-negative bacteria, did not cause a greater decrease (P greater than .05) in ammonia than monensin, an ionophore that is primarily effective against Gram-positive bacteria, it seemed that the "protein sparing" of monensin could largely be explained by its inhibition of Gram-positive bacteria.

Adaptation of protein synthesis to protein diets in rats.

Abstract: Protein synthesis and breakdown may change with alterations in diet, especially in response to altered protein intakes [1]. But studies of the dietary effects on protein metabolism were mainly concentrated on the response to a prolonged period after dietary change and on low protein diets. It has been demonstrated that acute supply of amino acids enhances the incorporation of amino acids into proteins. Moreover, protein synthesis rates change with the intermittent ingestion of protein meals [1–3]. Little, however, is known concerning changes in protein metabolic parameters during adaptation in response to an altered protein diet. The present study gives some preliminary information about changes in fractional rates of protein synthesis in liver and skeletal muscle after different time intervals of exchanging a pelleted standard diet by qualitatively different isonitrogenous experimental protein diets.