Responses in the absorptive phase in muscle and liver protein synthesis rates of growing rats

• Published in: Archiv für Tierernährung 1999, Vol.52 (1), p.41-52
• Main Authors: DSnicke, S, Nieto, R, Lobley, G.E, Fuller, M.F, Brown, D.S, Milne, E, Calder, A.G, Chen, S, Grant, I, B÷ttcher, W
• Format: Article
• Language: English
• Subjects: Amino Acids - metabolism; Animals; Eating; FEED INTAKE; FOIE; HIGADO; INGESTION DE PIENSOS; Intestinal Absorption; ISOTOPE RADIOACTIF; LIVER; Liver - metabolism; Male; Mass Spectrometry; MUSCLE; Muscle Proteins - biosynthesis; Muscle, Skeletal - metabolism; MUSCLES; MUSCULOS; Nitrogen Isotopes; Phenylalanine - metabolism; Postprandial response; PRISE ALIMENTAIRE (ANIMAUX); Protein Biosynthesis; PROTEIN SYNTHESIS; RADIOISOTOPES; RADIOISOTOPOS; RAT; RATA; RATS; SINTESIS DE PROTEINAS; Stable isotopes; SYNTHESE PROTEIQUE; TEMPS; TIEMPO; TIME; Time Factors
• ISSN: 0003-942X
• DOI: 10.1080/17450399909386150

The effect of time after beginning of a meal (30, 60, 90 and 120 min) on liver and gastrocnemius muscle protein synthesis was tested in growing male rats using the large dose technique, based on a 10 min exposure to [ 15 N]phenylalanine. The fractional synthesis rate was estimated from the ratio between the atom percent excess of tissue protein-bound and free labelled phenylalanine. The latter was measured by gas chromatography mass spectrometry using the tertiary-butyldimethylsilyl amino acid derivatives. The protein-bound phenylalanine of gastrocnemius muscle was separated from the other amino acids using preparative amino acid chromatography and then oxidised to N 2 in an automated carbon-nitrogen Roboprep (CN) combustion module attached to a continuous flow isotope ratio mass spectrometer (IRMS), with m/z ions 28 and 29 monitored. The protein-bound phenylalanine from liver was separated by a gas Chromatograph attached to a sample preparation module and an isotope ratio mass spectrometer (GC-C-IRMS), with again m/z ions of 28 and 29 monitored. The following results were obtained: the daily fractional protein synthesis rates (k s ) in gastrocnemius muscle and liver were 13.9% and 65.6% respectively, in 12h fasted 145 g rats. These k s increased within 30 min after ingestion of meal to 14.9% and 91.8% for muscle and liver, respectively, and remained at these values for the next 90 min (14.6% and 87.4% at 60 min, and 14.3% and 88.6% at 120 min after the beginning of feeding). It was concluded that measurement of protein synthesis rates characteristic for the absorptive phase can be undertaken in a period from thirty minutes to two hours after start of a meal, without significant changes in the k s values.