rhIGF-I/IGFBP-3 complex, but not free rhIGF-I, supports muscle protein biosynthesis in rats during semistarvation.

• BACKGROUND: The aim of this study was to evaluate the effect of insulin like growth factor-I (rhIGF-I) in complex with binding protein 3 (IGFBP 3) compared to the effect of free IGF-I on muscle protein biosynthesis in undernourished animals. METHODS: Three groups of female Sprague-Dawley rats (200 g) were initially semi-starved for 3 days and then treated with saline (controls), rhIGF-I (1 microg g-1) or equimolar amounts of rhIGF-I/rhIGFBP-3 complex (5 microg g-1) i.v. twice daily for 3 days during continuous semistarvation. Protein metabolism in hind limb skeletal muscle was studied by incorporation of L-[14C-U]phenylalanine into proteins, western blot determination of translation initiation factors involved in the binding of the 40S ribosomal subunit to mRNA, and quantification of mRNA content for IGF-I, IGF-IR and GH-R. Plasma measurements of insulin, IGF-I and amino acids were also performed. RESULTS: rhIGF-I/rhIGFBP-3, but not rhIGF-I alone, stimulated protein synthesis by 177 +/- 26% (P

Nyckelord

Amino Acids

blood

Animal Nutritional Physiological Phenomena

Animals

Blood Glucose

Carbon Radioisotopes

diagnostic use

Carrier Proteins

Energy Intake

Eukaryotic Initiation Factor-4E

Female

Gene Expression

physiology

Insulin

blood

Insulin-Like Growth Factor Binding Protein 3

metabolism

Insulin-Like Growth Factor I

genetics

metabolism

Muscle Proteins

biosynthesis

Muscle

Skeletal

metabolism

Peptide Initiation Factors

metabolism

Phosphoproteins

metabolism

Phosphorylation

RNA

Messenger

analysis

Rats

Rats

Sprague-Dawley

Starvation

metabolism

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