EFFECT OF SOMATOTROPIN ON NONESTERIFIED FATTY-ACID AND GLYCEROL METABOLISM IN GROWING PIGS

Eight crossbred barrows (71 kg initial BW) were allocated to two treatments involving daily i.m. injections of either excipient (control) or recombinantly derived porcine somatotropin (120-mu-g/kg of BW). On d 8 of treatment, beginning 15 h after injection, glycerol and nonesterified fatty acid (NEFA) kinetics were determined using a primed, continuous infusion of [2-H-3]glycerol and [9,10(n)-H-3]oleic acid. Kinetics were examined under both basal conditions and during a hyperinsulinemic/euglycemic clamp. Plasma concentrations of NEFA and glycerol and their respective entry rates were highly correlated. Insulin had no effect on plasma glycerol or glycerol entry rate, probably due to the very low rates that were observed in both the control and somatotropin-treated pigs. However, both plasma NEFA and oleic acid entry rate were reduced during hyperinsulinemia. Although indices of fat mobilization tended to be higher in pigs treated with somatotropin, the magnitude of the increases were small and would be sufficient to account for only a minor fraction of the decreased lipid accretion observed in somatotropin-treated pigs.