Insulin amino acid transport affected

GH stimulates incorporation of labelled amino acids into protein in skeletal muscle (diaphragm) from hypophysectomized rats in vitro [41,84], The effect is a consequence of stimulation of protein biosynthesis, although amino acid transport is also affected. Insulin and somatomedins also stimulate protein synthesis in diaphragm [44], but there are clear-cut differences between the actions of these hormones and of GH. Thus a 30 min lag period is characteristic of the action of GH, as is a refractory. period after 2-3 h of stimulation. 

Aside from inorganic ions, amino acids and other small organic molecules have transport systems to move them across membranes. Human erythrocytes have two different amino acid transporters, and both of them are affected by harmaline, though in different ways [529]. Caffeine and theophylline both inhibit glucose uptake by insulin-treated adipocytes [530],... 

The metabolic actions are complex. It will be stated here only that they include metabolism of fats, proteins, and, particularly relevant to diabetes, carbohydrates, specifically d-glucose. The effects insulin produces include increased membrane transport of glucose, amino acids, and K+. The activities of many intracellular enzymes are also affected, yet even polymer-coupled insulin molecules that are clearly unable to penetrate into the cell themselves still control these intracellular functions. The explanation with the most evidence is that all these insulin-mediated effects interact with specific insulin receptors on the surface of the cellular membranes. The receptor has been characterized to a considerable degree. It consists of two a and two P subunits connected by disulfide bonds. The search for the identity of putative second messengers has not yet established a proven candidate. 

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