Porcine Growth Hormone and LongR3IGF-I Can Improve Recovery from Surgery-Induced Weight Loss in Guinea Pigs

Abstract

In the present study, porcine growth hormone (pGH) and LongR3IGF-I (LR3IGF-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 LR3IGF-I administration. The pGH and LR3IGF-I were infused at rates of 400 μg/day (0.93 mg/kg/day) and 120 μg/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 LR3IGF-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 LR3IGF-I improved feed conversion efficiency. LR3IGF-I alone or in combination with pGH significantly increased the fractional weight of kidneys at the end of the 7-day treatment period, whereas LR3IGF-I alone increased the fractional weight of spleens. Concentrations of IGF-I in serum collected after 7 days of treatment were decreased by LR3IGF-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 LR3IGF-I are capable of enhancing the recovery of body weight lost in response to surgery in the guinea pig.