Effects of growth hormone and an antiserum to rat growth hormone on serum IGF-I and muscle protein synthesis and accretion in the rat.
Rats were injected twice daily for up to 10 days with GH or with a polyclonal antiserum to rat GH, commencing at 21-22 days of age. Administration of bovine or human GH (1mg/day) improved whole body growth rates by 22% and 29% respectively. Plantaris muscle mass was also increased, by 7 and 14% respectively. Anti-GH injected twice daily resulted in a 7% decrease in body weight at 4 days and a 10% reduction by 10 days. Similar decreases were observed in the total protein content of plantaris and soleus muscles. The decrease in the fractional rate of protein synthesis was proportionately greater than the decline in protein content in plantaris muscle whereas in the soleus no change in the rate of protein synthesis was observed, suggesting that the effect on this muscle was due to an increase in the rate of protein degradation. Serum total IGF-I was unchanged by treatment with either GH or anti-GH while the amount of hepatic IGF-I mRNA was also unaffected by anti-GH injection. These data are consistent with a direct effect of GH or an effect mediated by an autocrine/paracrine mechanism of action on muscle but do not support a role for serum total IGF-I as an endocrine mediator of GH action.
Palmer
R M
RM
Rowett Research Institute, Bucksburn, Aberdeen, U.K.
Flint
D J
DJ
MacRae
J C
JC
Fairhurst
F E
FE
Bruce
L A
LA
Mackie
S C
SC
Lobley
G E
GE
D000818:Animals; D015152:Blotting, Northern; D013006:Growth Hormone / Q000276:immunology / Q000494:pharmacology*; D007106:Immune Sera / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis / Q000378:metabolism*; D012313:RNA / Q000032:analysis; D051381:Rats; D011919:Rats, Inbred Strains
D007106:Immune Sera; D009124:Muscle Proteins; D012313:RNA; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone