Ceppi A, Mullis P E, Eggenberger E, Blum J W
Division of Nutrition Pathology, Institute of Animal Breeding, Berne, Switzerland.
Ann Nutr Metab. 1994;38(5):281-6. doi: 10.1159/000177822.
In calves with severe iron (Fe) deficiency, insulin-like growth factor (IGF)-I levels and IGF-I responses to exogenous growth hormone (GH) are reduced, while insulin-dependent glucose utilization is enhanced. Blood plasma concentrations of immunoreactive insulin (IRI), IGF-I, IGF-II and GH, and the half-life of blood plasma GH [after an i.v. injection of recombinant bovine GH (rbGH; 100 micrograms rbGH/kg body weight)] were measured in 20 calves at body weights between 160 and 190 kg. Calves were fed milk replacers containing 50 or 10 mg Fe/kg (groups Fe50 and Fe10, respectively). Daily weight gain and feed utilization were similar in both groups. Group Fe10 developed mild Fe deficiency anemia and blood plasma urea-nitrogen concentrations were higher (p < 0.05) than in group Fe50. IGF-I and IGF-II concentrations did not vary consistently over a 10-hour period and were not significantly influenced by different Fe intakes. The IRI concentration increased transiently (p < 0.05) after feed intake, but the total response was (not significantly) smaller in Fe-deficient calves. Plasma GH concentration changed episodically and was similar in both groups. Loss of GH from the circulation after i.v. rbGH injection, estimated by biexponential analysis, during the distribution or alpha phase (first 16 min) was similar in both groups, but during the beta phase was shorter (p < 0.05) in group Fe10 than in group Fe50 (29.9 and 34.2 min, respectively). The increased disappearance rate of GH, seen even in mild Fe deficiency, may contribute to reduced GH levels and IGF-I responses to GH in severe Fe deficiency.
在患有严重缺铁的犊牛中，胰岛素样生长因子（IGF）-I水平以及IGF-I对外源生长激素（GH）的反应降低，而胰岛素依赖的葡萄糖利用增强。对20头体重在160至190千克之间的犊牛，测定了血浆中免疫反应性胰岛素（IRI）、IGF-I、IGF-II和GH的浓度，以及静脉注射重组牛生长激素（rbGH；100微克rbGH/千克体重）后血浆GH的半衰期。给犊牛饲喂含铁量分别为50或10毫克/千克的代乳品（分别为Fe50组和Fe10组）。两组的日增重和饲料利用率相似。Fe10组出现轻度缺铁性贫血，血浆尿素氮浓度高于Fe50组（p<0.05）。IGF-I和IGF-II浓度在10小时内没有持续变化，且不受不同铁摄入量的显著影响。进食后IRI浓度短暂升高（p<0.05），但缺铁犊牛的总反应较小（无显著差异）。血浆GH浓度呈间歇性变化，两组相似。通过双指数分析估计，静脉注射rbGH后，在分布或α期（最初16分钟）两组循环中GH的损失相似，但在β期Fe10组比Fe50组短（p<0.05）（分别为29.9分钟和34.2分钟）。即使在轻度缺铁时也可见到的GH消失率增加，可能导致严重缺铁时GH水平降低以及IGF-I对GH的反应减弱。
