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Liver and other organs

FIGURE 19-1 Somatomedin hypothesis of growth hormone (GH) action. The direct actions of GH include diabetogenic and lipolytic actions and stimulatory action on several hepatic enzymes. These direct actions are antagonistic to insulin and often synergistic with Cortisol. The anabolic and growth-promoting actions of GH are mediated through the somatomedins. IGF-I participates in the negative feedback on GH secretion at the hypothalamic level by stimulating somatostatin production and at the pituitary level by directly blocking the effect of GH-releasing hormone on the expression of the GH gene. Reproduced with permission from Russell, W. E., and Van Wyk, J. J. (1995). Peptide growth factors. In "Endocrinology" (L. J. DeGroot, ed.), 3rd ed„ Vol. 1, pp. 2590-3623. W.B. Saunders Co., Philadelphia, PA.

FIGURE 19-1 Somatomedin hypothesis of growth hormone (GH) action. The direct actions of GH include diabetogenic and lipolytic actions and stimulatory action on several hepatic enzymes. These direct actions are antagonistic to insulin and often synergistic with Cortisol. The anabolic and growth-promoting actions of GH are mediated through the somatomedins. IGF-I participates in the negative feedback on GH secretion at the hypothalamic level by stimulating somatostatin production and at the pituitary level by directly blocking the effect of GH-releasing hormone on the expression of the GH gene. Reproduced with permission from Russell, W. E., and Van Wyk, J. J. (1995). Peptide growth factors. In "Endocrinology" (L. J. DeGroot, ed.), 3rd ed„ Vol. 1, pp. 2590-3623. W.B. Saunders Co., Philadelphia, PA.

II, which are apparently different from the sites to which IGF-I binds. The /3-subunits of both receptors contain a tyrosine kinase and ligand binding triggers the activity of the tyrosine kinase, resulting in autopho-sphorylation on tyrosine residues. Other proteins may be phosphorylated on tyrosine residues by the receptor kinase. IGF-I receptors are present in most tissues: the hormone exerts its effect in concert with other hormones produced in specialized tissues, and the IGF-I receptor is down-regulated after ligand binding in a typical process characteristic of many membrane receptors. IGF-II receptors bind IGF-II nearly exclusively and interact poorly with IGF-I. On the other hand, as has already been pointed out, IGF-II can bind to the IGF-I receptor and this interaction is important in humans, who, in contrast to some rodents, produce IGF-II. The IGF-II receptor is identical to the mannose 6-phosphate receptor and contains separate domains for binding IGF-II and mannose 6-phosphate. Interestingly, the mannose 6-phosphate-binding domain activates the TGF-/3 precursor by removing mannose, and this domain has other activities as well. The interaction of IGF-II with the IGF-II receptor may lead to the uptake of extracellular calcium possibly mediated by a G protein.

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Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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