In the present study, porcine
growth hormone (pGH) and LongR(3)IGF-I (LR(3)IGF-I), a potent analogue of
IGF-I, were infused continuously into 430-g guinea pigs for 7 days, either alone or in combination, to examine whether pGH can counteract the reduction in circulating
IGF-I concentrations induced by
LR(3)IGF-I administration. The pGH and
LR(3)IGF-I were infused at rates of 400 microg/day (0.93 mg/kg/day) and 120 microg/day (0.28 mg/kg/day), respectively, by miniosmotic pumps. The same doses were infused in the combination treatment. During the first day of treatment, animals lost between 2 and 3% of
body weight. Cumulative
body weight gains as a percentage of initial
body weight were significantly (P < 0.001) increased relative to vehicle-treated controls by the
LR(3)IGF-I, pGH, and combination treatments when effects were analyzed across the whole 7-day treatment period. The increased
weight gains relative to controls were largely made on day 2, but these gains were not associated with increased water or feed intakes, indicating that pGH and
LR(3)IGF-I improved feed conversion efficiency.
LR(3)IGF-I alone or in combination with pGH significantly increased the fractional weight of kidneys at the end of the 7-day treatment period, whereas
LR(3)IGF-I alone increased the fractional weight of spleens. Concentrations of
IGF-I in serum collected after 7 days of treatment were decreased by
LR(3)IGF-I, but this decrease was not ameliorated by coinfusion with pGH. GH alone did not have any effects on
IGF-I concentration. This study suggests that pGH does not have a strong influence on circulating
IGF-I concentrations in the guinea pig. We have also demonstrated that pGH and
LR(3)IGF-I are capable of enhancing the recovery of
body weight lost in response to surgery in the guinea pig.