Administration of growth hormone to pigs alters the relative amount of insulin-like growth factor-I mRNA in liver and skeletal muscle.
The relative amount of insulin-like growth factor-I (IGF-I) mRNA was determined in the liver and skeletal muscle of market weight crossbred barrows (castrated male pigs) using a solution hybridization-nuclease protection assay. Pigs were given either 50 micrograms recombinant porcine GH per kg body weight or vehicle daily for 24 days i.m. They were fed corn-soybean meal diets containing either 140 or 200 g crude protein/kg (low or high protein). The percentage of muscle in the carcasses of pigs given GH was greater (P less than 0.01) than that of controls. Relative to controls, GH increased (P less than 0.05) the amount of liver IGF-I mRNA by 2.7-fold in pigs fed the low protein diet and 3.0-fold in pigs fed the high protein diet. The amount of IGF-I mRNA in the muscles of GH-treated pigs was 77% and 84% of control pigs in those fed the low and high protein diets respectively (P less than 0.08). GH increased (P less than 0.001) the serum concentration of IGF-I 1.6-fold in pigs fed the low protein diet and 2.0-fold in those fed the high protein diet. These results indicate that the administration of GH to pigs influences the relative amount of liver IGF-I mRNA. The increased amount of liver IGF-I mRNA and the increased serum IGF-I concentrations suggest that IGF-I plays an endocrine role in mediating GH-induced muscle hypertrophy in pigs.
Department of Animal Science, Michigan State University, East Lansing 48824.
A L
AL
Grant
W G
WG
Helferich
S A
SA
Kramer
R A
RA
Merkel
W G
WG
Bergen
D000818:Animals; D001345:Autoradiography; D015152:Blotting, Northern; D004044:Dietary Proteins / Q000008:administration & dosage; D013006:Growth Hormone / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D008099:Liver / Q000737:chemistry* / Q000187:drug effects; D008297:Male; D009132:Muscles / Q000737:chemistry* / Q000187:drug effects; D012333:RNA, Messenger / Q000032:analysis*; D013552:Swine / Q000097:blood / Q000502:physiology*
D004044:Dietary Proteins; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone