To measure actin/myosin protein breakdown, the 24 h excretion of Nτ-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-2H3]histidine, L-[phenyl-2H5]phenylalanine and L-[phenyl-2H2]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.
Measuring whole-body actin/myosin protein breakdown in mice using a primed constant stable isotope-infusion protocol
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Yvonne L. J. VISSERS, Maarten F. VON MEYENFELDT, Valeria B. BRAULIO, Yvette C. LUIKING, Nicolaas E. P. DEUTZ; Measuring whole-body actin/myosin protein breakdown in mice using a primed constant stable isotope-infusion protocol. Clin Sci (Lond) 1 June 2003; 104 (6): 585–590. doi: https://doi.org/10.1042/CS20020283
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