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Effects of intermittent growth hormone or insulin-like growth factor 1 administration in the neonatal dwarf rat
G R Ambler1, B H Breier, S N McCutheon
1Department of Paediatrics, University of Auckland, New Zealand.
Insights
Growth hormone (GH) administration significantly enhanced growth parameters in neonatal rats. This study highlights the anabolic role of GH during early development, impacting fetal and neonatal growth.
Area of Science:
- Endocrinology
- Neonatal Physiology
- Growth Factor Research
Background:
- The role of growth hormone (GH) in neonatal development is not fully understood.
- Neonatal GH deficiency can impact early growth and development.
- Investigating the effects of exogenous GH and IGF-1 is crucial for understanding neonatal growth regulation.
Purpose of the Study:
- To evaluate the impact of growth hormone (GH) and insulin-like growth factor 1 (IGF-1) administration on neonatal growth parameters.
- To assess the effects on serum IGF-1 levels, body composition, and hepatic GH receptor binding in neonatal rats.
- To elucidate the anabolic role of GH during the neonatal period.
Main Methods:
- Neonatal GH-deficient rats received daily subcutaneous injections of bovine GH (bGH), human IGF-1, or saline from day 2 to day 12 of life.
- Growth parameters, including body weight gain, were monitored.
- Serum IGF-1 concentration, body composition (carcass nitrogen and water), and hepatic GH receptor binding were analyzed.
Main Results:
- bGH treatment led to significant increases in body weight gain, serum IGF-1, carcass nitrogen, and carcass water compared to IGF-1 or saline groups.
- No significant differences were observed between IGF-1 and saline-treated groups for these parameters.
- Hepatic GH receptor binding was significantly lower in bGH-treated animals.
Conclusions:
- GH administration demonstrates anabolic effects in the neonatal period.
- These findings suggest a critical role for GH in fetal and neonatal growth.
- Exogenous GH effectively promotes growth in neonatal GH-deficient rats, though it downregulates hepatic GH receptor binding.
Abstract:
To further evaluate the role of growth hormone (GH) in the neonatal period, the effects of GH or insulin-like growth factor 1 (IGF-1) administration were studied in the neonatal GH-deficient rat. Groups of pups from newborn litters were randomized to receive twice daily subcutaneous injections of recombinant bovine growth hormone (bGH, 5 micrograms), recombinant human IGF-1 (10 micrograms) or saline from the second to twelfth day of life. The effects on growth parameters, serum IGF-1 concentration, body composition and hepatic GH receptor binding were assessed. bGH-treated animals showed increases in body weight gain (p = 0.01), serum IGF-1 (p < 0.01), carcass nitrogen (p < 0.001) and carcass water (p < 0.001) compared to IGF-1 or saline-treated animals. No differences in these parameters were noted between IGF-1 and saline-treated groups. bGH-treated animals showed a significantly lower hepatic GH receptor binding (p < 0.01) compared to the other two groups. The demonstration of anabolic responses to GH administration in the neonatal period has implications for the possible role of GH in fetal and neonatal growth.