Effects of food deprivation and refeeding on total protein and actomyosin degradation.

J. B. Li, Steven Wassner

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Total protein and actomyosin degradation rates were determined in perfused rat hemicorpus preparations. By simultaneously measuring the release of two nonmetabolizable amino acids phenylalanine and N tau-methylhistidine from the hemicorpus, the respective rates of total protein and actomyosin degradation could be calculated. When rats were deprived of food for 48 h, the rate of total protein degradation increased to 148% of the fed controls. If rats were food deprived and then refed for 24 h, the degradation rate decreased to only 79% of the rate of fed controls. Measurement of N tau-methylhistidine release indicated that food deprivation led to a dramatic increase in the rate of actomyosin degradation (427% of fed), whereas refeeding decreased the actomyosin degradation rate to that of the fed controls. Calculations of the fractional degradation rates show that actomyosin breaks down at a much slower rate than the nonactomyosin proteins (1.5 vs. 20.8%/day in preparations from fed rats, and 6.2 vs. 28.2%/day in preparations from food-deprived rats). Therefore, the contribution of actomyosin breakdown to total muscle protein breakdown is small in the fed state (11%) and increased threefold after food deprivation. The addition of insulin to the perfusion medium decreased the rate of total protein degradation by 18% in preparations from food-deprived rats with no significant effect on actomyosin degradation. Thus, in vitro, insulin's major effect may be to decrease the degradation of more rapidly turning over, nonactomyosin proteins. Protein degradation, as well as protein synthesis, contributes to the adaptation of muscle to starvation and refeeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Original languageEnglish (US)
JournalThe American journal of physiology
Volume246
Issue number1 Pt 1
StatePublished - Jan 1 1984

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Food Deprivation
Actomyosin
Proteolysis
Food
Proteins
Muscle Proteins
Starvation
Phenylalanine
Perfusion
Insulin
Amino Acids
Muscles

All Science Journal Classification (ASJC) codes

  • Physiology (medical)

Cite this

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title = "Effects of food deprivation and refeeding on total protein and actomyosin degradation.",
abstract = "Total protein and actomyosin degradation rates were determined in perfused rat hemicorpus preparations. By simultaneously measuring the release of two nonmetabolizable amino acids phenylalanine and N tau-methylhistidine from the hemicorpus, the respective rates of total protein and actomyosin degradation could be calculated. When rats were deprived of food for 48 h, the rate of total protein degradation increased to 148{\%} of the fed controls. If rats were food deprived and then refed for 24 h, the degradation rate decreased to only 79{\%} of the rate of fed controls. Measurement of N tau-methylhistidine release indicated that food deprivation led to a dramatic increase in the rate of actomyosin degradation (427{\%} of fed), whereas refeeding decreased the actomyosin degradation rate to that of the fed controls. Calculations of the fractional degradation rates show that actomyosin breaks down at a much slower rate than the nonactomyosin proteins (1.5 vs. 20.8{\%}/day in preparations from fed rats, and 6.2 vs. 28.2{\%}/day in preparations from food-deprived rats). Therefore, the contribution of actomyosin breakdown to total muscle protein breakdown is small in the fed state (11{\%}) and increased threefold after food deprivation. The addition of insulin to the perfusion medium decreased the rate of total protein degradation by 18{\%} in preparations from food-deprived rats with no significant effect on actomyosin degradation. Thus, in vitro, insulin's major effect may be to decrease the degradation of more rapidly turning over, nonactomyosin proteins. Protein degradation, as well as protein synthesis, contributes to the adaptation of muscle to starvation and refeeding.(ABSTRACT TRUNCATED AT 250 WORDS)",
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Effects of food deprivation and refeeding on total protein and actomyosin degradation. / Li, J. B.; Wassner, Steven.

In: The American journal of physiology, Vol. 246, No. 1 Pt 1, 01.01.1984.

Research output: Contribution to journalArticle

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AB - Total protein and actomyosin degradation rates were determined in perfused rat hemicorpus preparations. By simultaneously measuring the release of two nonmetabolizable amino acids phenylalanine and N tau-methylhistidine from the hemicorpus, the respective rates of total protein and actomyosin degradation could be calculated. When rats were deprived of food for 48 h, the rate of total protein degradation increased to 148% of the fed controls. If rats were food deprived and then refed for 24 h, the degradation rate decreased to only 79% of the rate of fed controls. Measurement of N tau-methylhistidine release indicated that food deprivation led to a dramatic increase in the rate of actomyosin degradation (427% of fed), whereas refeeding decreased the actomyosin degradation rate to that of the fed controls. Calculations of the fractional degradation rates show that actomyosin breaks down at a much slower rate than the nonactomyosin proteins (1.5 vs. 20.8%/day in preparations from fed rats, and 6.2 vs. 28.2%/day in preparations from food-deprived rats). Therefore, the contribution of actomyosin breakdown to total muscle protein breakdown is small in the fed state (11%) and increased threefold after food deprivation. The addition of insulin to the perfusion medium decreased the rate of total protein degradation by 18% in preparations from food-deprived rats with no significant effect on actomyosin degradation. Thus, in vitro, insulin's major effect may be to decrease the degradation of more rapidly turning over, nonactomyosin proteins. Protein degradation, as well as protein synthesis, contributes to the adaptation of muscle to starvation and refeeding.(ABSTRACT TRUNCATED AT 250 WORDS)

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