EXOGENOUS GROWTH-HORMONE STIMULATES SOMATOTROPIC AXIS FUNCTION AND GROWTH IN NEONATAL PIGS

We studied the effects of exogenous porcine growth hormone (pGH) admin istration on circulating insulin-like growth factor I (IGF-I) concentr ation, IGF-binding proteins (IGFBP), tissue growth, and protein synthe sis in neonatal pigs. One-day-old pigs were given daily intramuscular injections of either pGH (1 mg/kg body wt) (n = 6) or saline (n = 5) f or 7 days, after which time we measured in vivo protein synthesis usin g a bolus of [H-3]-phenylalanine. Mean plasma pGH concentration in pGH -treated pigs measured on day 7 was 22-fold higher than in controls. T he plasma IGF-I concentration in pGH-treated pigs was significantly gr eater than in controls after 1 day of treatment and plateaued at 285% of control values after 4 days. After 7 days of treatment, plasma IGFB P-3 concentrations and the plasma glucose response to a meal were also greater in pGH-treated than control pigs. pGH treatment significantly increased body weight gain and food conversion efficiency and the pro tein synthesis rate in several visceral organs. Our results demonstrat e that exogenous pGH increases circulating IGF-I and IGFBP-3 concentra tions and visceral organ growth in neonatal pigs, suggesting that the somatotrophic axis is functional in the neonate.