title: Measuring whole-body actin/myosin protein breakdown in mice using a primed constant stable isotope-infusion protocol.
abstract: To measure actin/myosin protein breakdown, the 24 h excretion of N (tau)-methylhistidine (3MH) is used. However, in mice, this method is invalid. Therefore we have developed a liquid chromatography-MS technique to measure the tracer/tracee ratio and concentration of 3MH in plasma, enabling an in vivo primed constant infusion protocol with a deuterated stable isotope of 3MH. We tested this model by giving a primed constant infusion of L-[3-methyl-(2)H(3)]histidine, L-[phenyl-(2)H(5)]phenylalanine and L-[phenyl-(2)H(2)]tyrosine to three anaesthetized experimental groups: mice receiving saline intraperitoneally (i.p.) (CON), mice receiving saline i.p. and starved for 9 h (STA), and mice receiving lipopolysaccharide i.p. and starved for 9 h (STA+LPS). The contribution of myofibrillar to total protein breakdown was significantly lower in the STA group than the CON group (30+/-4% and 54+/-14% respectively; P <0.05), and was significantly higher in the STA+LPS group than the STA group (52+/-7% and 30+/-4% respectively; P <0.05). Whole-body myofibrillar protein breakdown, total protein breakdown, protein synthesis and net protein breakdown were not different between the groups. We conclude that this in vivo primed constant stable isotope-infusion protocol can give valuable information about the role of actin/myosin protein breakdown in mice.
authors.affiliation: Department of Surgery, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands.
authors.forename: Yvonne L J
authors.initials: YL
authors.lastname: Vissers
authors.forename: Maarten F
authors.initials: MF
authors.lastname: von Meyenfeldt
authors.forename: Valeria B
authors.initials: VB
authors.lastname: Braulio
authors.forename: Yvette C
authors.initials: YC
authors.lastname: Luiking
authors.forename: Nicolaas E P
authors.initials: NE
authors.lastname: Deutz
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D001835:Body Weight; D002853:Chromatography, Liquid; D003903:Deuterium; D007262:Infusions, Intravenous; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D013058:Mass Spectrometry; D008762:Methylhistidines / Q000097:blood; D051379:Mice; D008815:Mice, Inbred Strains; D023421:Models, Animal; D009132:Muscles / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism*; D010649:Phenylalanine; D011849:Radioactive Tracers; D013217:Starvation / Q000378:metabolism*; D014443:Tyrosine
chemical_list: D000199:Actins; D008070:Lipopolysaccharides; D008762:Methylhistidines; D011849:Radioactive Tracers; D014443:Tyrosine; D010649:Phenylalanine; D003903:Deuterium; D009218:Myosins