Epinephrine, effect glucose release

SYMPATHOMIMETICS-EPINEPHRINE ANTIDIABETIC DRUGS May t antidiabetic therapy requirement Epinephrine causes the release of glucose from the liver and is an important defence/homeostatic mechanism. Hyperglycaemia may occur due to an antagonistic effect Larger doses of antidiabetic therapy may be needed during the period of epinephrine use, which is usually in the short term or in emergency situations... 

Activation of Gs or Gi proteins results in stimulation or inhibition, respectively, of adenylyl cyclase which catalyses the formation of cyclic adenosine monophosphate (cAMP) from ATP The cAMP binds to protein kinase A (PKA), which mediates the diverse cellular effects of cAMP by phosphorylating substrate enzymes, thereby increasing their activity. Among the responses mediated by cAMP are increases in contraction of cardiac and skeletal muscle and glycogenolysis in the liver by adrenaline (epinephrine). Because a single activated receptor can cause the conversion of up to 100 inactive Gs proteins to the active form, and each of these results in the synthesis of several hundred cAMP molecules, there is a very considerable signal amplification. For example, adrenaline concentrations as low as 10-10 M can stimulate the release of glucose sufficient to increase... 

The initial suppression of insulin response is probably mediated through increased epinephrine and sympathetic activity in view of the observation that an infusion of epinephrine can suppress insulin release following a glucose infusion in normal subjects (P2). This effect can be blocked by phentolamine. 

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