Effects of isoproterenol infusion on the hindlimb metabolism of growing wether lambs

The effect of a mixed beta 1/beta 2-adrenergic agonist, isoproterenol, on hindlimb metabolism was studied in growing wether lambs using arteriovenous difference and blood flow rate techniques. Isoproterenol (48 micrograms kg-1 d-1), or saline, was infused into a jugular vein of five wether lambs (30 to 35 kg) for five days and samples taken on the fifth day of treatment. Infusion of isoproterenol significantly increased blood flow, oxygen uptake and tyrosine uptake across the hindlimb. Hindlimb non-esterified fatty acid uptake was increased but not significantly (P = 0.11) and arterial growth hormone concentration was not altered by isoproterenol infusion. Results suggest that beta-adrenergic agonists promote lean tissue deposition by increased muscle blood flow rate and amino acid uptake.