THE EFFECT OF GH AND IGF-I ADMINISTRATION ON GROWTH DURING MATURATION

Autor: M Lu, Mark R. Benedict, R R Richman
Rok vydání: 1993
Předmět:
Zdroj: Pediatric Research. 33:S68-S68
ISSN: 1530-0447
0031-3998
DOI: 10.1203/00006450-199305001-00388
Popis: To evaluate the growth promoting effects of GH and IGF-I in normal animals, we infused vehicle (0.1 M acetic acid), twine GH (3.3 mg/kg/day), or recomhinanl human IGF-I (1,2 mg/kg/day) (n = 5 per group) for 2 weeks via indwelling osmotic minipumps to Fischer 344 male rats, aged 2 (immature) and 8 mo (mature). Regardless of the treatment, all immature rats grew rapidly, gaining approximately 40 g per week. Mature, control and IGF-lrealed rats gained about 10 g/wk; GH-treatcd rats exhibited virtually no growth. Basal serum IGF-I levels had increased by 20% between 2 and 8 mo. Following infusion of IGF-I, the levels increased 24% and 43% in immature and mature rats, respectively, while GH administration resulted in an 8% and 26% decrease in IGF-I levels. The pattern of the IGF binding protein (BP) bands observed using ligand blotting were typical for rodent serum. In mature control animals, BP-3 levels more than doubled and BP-2 levels had tripled compared to immature rats. While IGF-I administration had little effect on BP-3 levels, it tripled BP-2 levels at 2 mo, but suppressed the expected age-related increase. GH administration had little effect on the BPs at either age. In conclusion, during maturation, there was a striking inverse relationship between growth rates, which fell sharply, and IGF BP levels, which rose; serum IGF-I increased only slightly during this period. IGF-I infusion resulted in a differential increase wilh age in total serum IGF-I levels, suggesting that the clearance rate of exogenous IGF-I, and perhaps, its bioavailabilily, may decrease towards the end of the period of rapid growth. If so, then the rise in BP levels may play a rule in the deceleration in growth which occurs during maturation.
Databáze: OpenAIRE
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