Insulin-like growth factor I stimulates cardiac myosin heavy chain and actin synthesis in the awake rat.
To determine the effect of insulin-like growth factor I (IGF-I) on cardiac contractile protein synthesis in vivo, we measured L-[ring-2, 6-3H]phenylalanine incorporation into myosin heavy chain and actin during intravenous infusions (4 h) of either saline or IGF-I (1 microgram. kg-1. min-1) in awake rats. After an overnight fast, IGF-I increased myosin synthesis by 29% compared with saline (11.5 +/- 0.8 vs. 8.9 +/- 0.6%/day, P < 0.01) and actin synthesis by 26% (7.2 +/- 0.3 vs. 5.7 +/- 0.3%/day, P < 0.01), with similar effects in left and right ventricles and a comparable effect on mixed cardiac protein. When amino acids were infused with IGF-I, a further increase in myosin synthesis was observed (P < 0.01). In fed rats, despite higher baseline synthesis rates than in fasted rats (P < 0. 01), IGF-I also increased the synthesis of myosin (12.3 +/- 0.5 vs. 9.9 +/- 0.5%/day, P < 0.01) and actin (8.8 +/- 0.3 vs. 7.5 +/- 0. 2%/day, P < 0.01) compared with saline. IGF-I infusion had no hypoglycemic effect and did not change heart rate or blood pressure. Thus relatively low-dose IGF-I has a direct action in vivo to acutely increase heart contractile protein synthesis in both fasted and fed awake rats.
Young
L H
LH
Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
Renfu
Y
Y
Hu
X
X
Chong
S
S
Hasan
S
S
Jacob
R
R
Sherwin
R S
RS
D000199:Actins / Q000096:biosynthesis*; D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004435:Eating / Q000502:physiology; D005215:Fasting; D006439:Hemodynamics / Q000187:drug effects; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000096:biosynthesis*; D009994:Osmolar Concentration; D051381:Rats; D017207:Rats, Sprague-Dawley
D000199:Actins; D000596:Amino Acids; D004338:Drug Combinations; D007328:Insulin; D007334:Insulin-Like Growth Factor I; D018995:Myosin Heavy Chains