生长激素介绍 Growth Hormone

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Growth Hormone (Somatotropin)

• Naturally occurring protein hormone 自然产生
• Regulates body growth 调节身体增长
• Effects of GH 生长激素的作用
  
  • Direct 直接作用
    
    • Reduced glucose transport and metabolism 加快葡萄糖的运输和代谢
    • Increased lipolysis 增加脂类分解
    • Increased amino acid transport 增加氨基酸的运输
    • Increased protein synthesis 增加蛋白质的合成
    • Increased IGF-I production 增加样生长因子的产生
    • Increased fibroblast differentiation 增加纤维组织母细胞的分化
      
  • Indirect 间接作用
    
    • Promotion of growth and endocrine effects 促进生长和内分泌的效用
    • Reduction in insulin receptors in liver  减少肝脏中胰岛素受体
    • Localized decrease in adipose tissue 减少局部脂肪
      
      • free fatty acides released 自由脂肪酸释放
        
    • Increases in both transcription and translation 增加转录和翻译
    • Chondrocyte, osteoblast, and adipocyte formation 软骨细胞，成骨细胞，脂肪细胞形成。
      
  • Muscle Growth 肌肉的增长
    
    • increased rates of muscle protein synthesis 增加肌肉合成效率
    • decreased protein degradaion 减少肌肉分解
    • increased RNA and DNA 增加rna 和dna
      
      • often accompanying increased protein accretion 经常伴随蛋白质的增加
        
    • increased DNA is likely a result of increased satellite cell activity
      
  • Bone Growth 骨骼的增长
    
    • mediated through IGF-I 通过样生长因子调节
      
      • IGF-I
        
        • increases chrondrocyte proliferation 增加软骨细胞的增值
        • increases osteoblast activity 增加成骨细胞的活动
          
      • GH leads to increased bone length prior to epipyseal closure
      • GH increases periosteal growth contribuing to increased bone mass
        
• Regulation of Growth Hormone Secretion 调整生长激素的分泌
  
  • Events increasing rate of release
    
    • Starvation
      
      • Hypoglycemia
        
        • Acute hypoglycemia: potent stimulator of GH release
          
      • Low FA in blood
      • Severe chronic protein deprivation
        
        • high circulating GH levels
          
    • Stress
      
      • Excitement
      • Trauma
        
    • Exercise
    • Amino Acid Supplementation
      
      • Arginine, Orthanine
        
    • PreREM Sleep
      
  • Hypothalamus
    
    • Growth hormone releasing hormone
    • Somatostatin / growth hormone inhibitory hormone
      
  • Neurotransmitters increasing GH release
    
    • Catecholamines
    • Domamine
    • Serotonin
      
• Metabolic effects
  
  • Increased lipolysis
  • Increased protein synthisis
    
    • GH affect on muscle is mediated through IGF-I and binding sites for IGF-I
      
  • Decreased glucose use
  • Interacts with receptors on cell membrane
    
    • Liver, kidney, muscle
    • Causes release of IGF-I into circulation
      
      • inturn activates target tissue
      • various binding proteins are involved in transporting IGF-I to target tissue
        
  • Growth hormone is species specific
    
• IGF-I
  
  • can stimulate proliferation and differentiation of myoblasts
  • increases uptake of glucose and amino acides into muscle
  • negative feedback on pituitary
  • increases release of somatostatin
    

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