STUDIES ON IGF-I SIGNAL CASCADE ON MUSCLE PROTEIN RETENTION

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Influence of methionine and/or glycine deficiency on protein synthesis of chicken embryo myoblasts cultured in Medium 199 was examined. Protein synthesis cultured in Medium 199 in which all ingredients were solved in Dulbecco's modified phosphate buffered saline was dramatically lower than that in Medium 199 in which all ingredients were solved in water. Although methionine deficiency from Medium 199 decreased myoblast protein synthesis, glycine deficiency did not affect. There was no interaction between methionine and glycine deficiency on myoblast protein synthesis.The influence of leucine and fetal calf serum (FCS) in Medium 199 on protein synthesis and degradation of chicken embryo myoblasts was examined. Medium 199 included 0, 1, 2, 5, 10% FCS and 457 (original concentration of leucine in Medium 199), 2287, 4574μmol leucine/l. There was an interaction between leucine and FCS concentrations on muscle protein synthesis in vitro. When FCS was not included in Medium 199, myoblast prot … More ein synthesis was stimulated with an increment in leucine concentration in the medium from 2287 to 4574 μmol/l. When 1 or 2% of FCS was included in Medium 199, myoblast protein synthesis was stimulated by increasing leucine concentration in the medium from 457 to 2287 μmol/l, and at the higher level of leucine, protein synthesis was not stimulated. At more than 5% of FCS in the medium, myoblast protein synthesis at higher concentration of luecine of 4574μmol/l was significantly lower than those of lower leucine levels.No interaction between leucine and FCS concentrations on muscle protein degradation Was observed. Protein degradation of chicken embryo myoblasts was decreased by an increment of FCS concentration in the medium from 0 to 5%, and at the higher level no significant influence was observed. When leucine concentration of in the medium was increased from 457 to 2287μmol/l, protein degradation of chicken embryo myoblasts was decreased. But high concentration of leucine at 4457μmol/l did not affect protein degradation of chicken embryo myoblasts. Less