Failure of IGF-I infusion to promote growth in Zn deficient hypophysectomized rats.
The retarded growth of zinc-deficient rats is associated with low plasma insulin-like growth factor-I (IGF-I). To determine whether the low circulating IGF-I concentrations are responsible for the stunted growth, the growth response of zinc-deficient hypophysectomized rats to supplementation with recombinant human IGF-I (hIGF-I) was investigated. There were three dietary groups: zinc-deficient (0.9 mg zinc/kg diet), controls (66 mg zinc/kg diet) and zinc-adequate pair-fed (66 mg zinc/kg diet). All rats in each group received hIGF-I (150 micrograms/day) by subcutaneous infusion for 12 days, except for half of the animals in the control group which were sham-treated and which received vehicle infusion for the same period of time. The magnitude of the change was small, nevertheless infusion of hIGF-I significantly increased (p < 0.05) the body weight, tail length, liver weight and tibial epiphyseal width of control animals. This growth effect of hIGF-I was inhibited by lack of zinc in the diet, as evidenced by continuous weight loss, no increase in tail length and lowered tibial epiphyseal width in zinc-deficient animals. We conclude that systemic supplementation of hIGF-I can promote growth in hypophysectomized rats. The absence of weight gain and bone growth in zinc-deficient animals during the infusion period suggests that the growth promoting effect of circulating IGF-I is impaired by zinc deficiency.
Cha
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MC
School of Dietetics and Human Nutrition, McGill University, Ste. Anne de Bellevue, PQ, Canada.
Rojhani
A
A
D000469:Alkaline Phosphatase / Q000097:blood / Q000187:drug effects; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D019587:Dietary Supplements; D006130:Growth Disorders / Q000188:drug therapy*; D013006:Growth Hormone / Q000502:physiology; D006801:Humans; D007016:Hypophysectomy; D007260:Infusion Pumps; D007334:Insulin-Like Growth Factor I / Q000008:administration & dosage / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects; D008297:Male; D009929:Organ Size; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000494:pharmacology; D013977:Tibia / Q000187:drug effects; D015032:Zinc / Q000032:analysis / Q000172:deficiency* / Q000494:pharmacology
D011994:Recombinant Proteins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D000469:Alkaline Phosphatase; D015032:Zinc