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Divergent responses of serum insulin-like growth factor-I and liver growth hormone (GH) receptors to exogenous GH in protein-restricted rats. 1990

J P Thissen, and S Triest, and L E Underwood, and M Maes, and J M Ketelslegers
Unité de Diabétologie et Nutrition, University of Louvain School of Medicine, Brussels, Belgium.

Protein deprivation in young rats retards growth and decreases serum insulin-like growth factor-I (IGF-I) concentrations, neither of which is prevented by injections of GH once daily. Since four time daily injections of GH in hypophysectomized rats increase serum IGF-I concentrations more efficiently than single daily injections, we assessed whether this mode of GH delivery could overcome the GH resistance of protein malnutrition. Also, we evaluated whether continuous GH infusion could override this GH resistance. We fed 4-week-old female Wistar rats a low (5%) protein diet (P5) or a normal (15%) protein diet (P15) for 7 days. In a first experiment, rats fed a P5 diet received 40 or 400 micrograms/100 g BW.day rat GH (rGH) in four daily sc injections, while control P5 rats were injected at the same frequency with vehicle. In a second experiment, rats fed a P5 diet received 200 micrograms rGH/100 g BW.day by continuous infusion, while P5 sham-operated rats served as controls. IGF-I was measured by RIA on extracted serum, and free and total liver GH binding were determined by incubation of [125I]bovine GH with water- or MgCl2-treated homogenates, respectively. Neither continuous infusion nor repeated injections of rGH normalized the indices of growth or restored the serum IGF-I level to P15 control values. Injections of 400 micrograms rGH increased serum IGF-I 2-fold (P less than 0.01), but did not promote growth. Continuous GH infusion increased total and free liver GH binding to P15 control values, but had no effect on serum IGF-I. The discordance between liver GH binding and IGF-I confirms that a postreceptor defect is responsible for the GH resistance in protein restriction. These observations demonstrate that the consequences of protein restriction on growth are not overridden by intermittent or continuous administration of GH. The increase in IGF-I in response to 400 micrograms GH given intermittently in the absence of growth-promoting effects suggests that nutritional sufficiency is essential for IGF-I to promote growth.

UI MeSH Term Description Entries
D007334 Insulin-Like Growth Factor I A well-characterized basic peptide believed to be secreted by the liver and to circulate in the blood. It has growth-regulating, insulin-like, and mitogenic activities. This growth factor has a major, but not absolute, dependence on GROWTH HORMONE. It is believed to be mainly active in adults in contrast to INSULIN-LIKE GROWTH FACTOR II, which is a major fetal growth factor. IGF-I,Somatomedin C,IGF-1,IGF-I-SmC,Insulin Like Growth Factor I,Insulin-Like Somatomedin Peptide I,Insulin Like Somatomedin Peptide I
D008099 Liver A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances. Livers
D011488 Protein Deficiency A nutritional condition produced by a deficiency of proteins in the diet, characterized by adaptive enzyme changes in the liver, increase in amino acid synthetases, and diminution of urea formation, thus conserving nitrogen and reducing its loss in the urine. Growth, immune response, repair, and production of enzymes and hormones are all impaired in severe protein deficiency. Protein deficiency may also arise in the face of adequate protein intake if the protein is of poor quality (i.e., the content of one or more amino acids is inadequate and thus becomes the limiting factor in protein utilization). (From Merck Manual, 16th ed; Harrison's Principles of Internal Medicine, 12th ed, p406) Deficiency, Protein,Deficiencies, Protein,Protein Deficiencies
D011919 Rats, Inbred Strains Genetically identical individuals developed from brother and sister matings which have been carried out for twenty or more generations or by parent x offspring matings carried out with certain restrictions. This also includes animals with a long history of closed colony breeding. August Rats,Inbred Rat Strains,Inbred Strain of Rat,Inbred Strain of Rats,Inbred Strains of Rats,Rat, Inbred Strain,August Rat,Inbred Rat Strain,Inbred Strain Rat,Inbred Strain Rats,Inbred Strains Rat,Inbred Strains Rats,Rat Inbred Strain,Rat Inbred Strains,Rat Strain, Inbred,Rat Strains, Inbred,Rat, August,Rat, Inbred Strains,Rats Inbred Strain,Rats Inbred Strains,Rats, August,Rats, Inbred Strain,Strain Rat, Inbred,Strain Rats, Inbred,Strain, Inbred Rat,Strains, Inbred Rat
D011986 Receptors, Somatotropin Cell surface proteins that bind GROWTH HORMONE with high affinity and trigger intracellular changes influencing the behavior of cells. Activation of growth hormone receptors regulates amino acid transport through cell membranes, RNA translation to protein, DNA transcription, and protein and amino acid catabolism in many cell types. Many of these effects are mediated indirectly through stimulation of the release of somatomedins. Growth Hormone Receptors,Receptors, Growth Hormone,Somatomammotropin Receptors,Somatotropin Receptors,Growth Hormone Receptor,Receptor, Growth Hormone,Receptors, Somatomammotropin,Somatomammotropin Receptor,Somatotropin Receptor,Hormone Receptor, Growth,Hormone Receptors, Growth
D001835 Body Weight The mass or quantity of heaviness of an individual. It is expressed by units of pounds or kilograms. Body Weights,Weight, Body,Weights, Body
D002149 Energy Intake Total number of calories taken in daily whether ingested or by parenteral routes. Caloric Intake,Calorie Intake,Intake, Calorie,Intake, Energy
D004435 Eating The consumption of edible substances. Dietary Intake,Feed Intake,Food Intake,Macronutrient Intake,Micronutrient Intake,Nutrient Intake,Nutritional Intake,Ingestion,Dietary Intakes,Feed Intakes,Intake, Dietary,Intake, Feed,Intake, Food,Intake, Macronutrient,Intake, Micronutrient,Intake, Nutrient,Intake, Nutritional,Macronutrient Intakes,Micronutrient Intakes,Nutrient Intakes,Nutritional Intakes
D005260 Female Females
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia

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