MadSci Network: General Biology

Re: How does adrenaline play a part in the homeostasis of blood glucose?

Date: Sat May 6 08:43:02 2000
Posted By: Terry Hebert, Faculty, Universite de Montreal, Biochemistry, Montréal Heart Institute
Area of science: General Biology
ID: 957611150.Gb

Dear Vince,

That's a good question. You can find more details in any good college-level 
biochemistry text. Here goes: 

Both adrenaline and noradrenaline (catecholamine hormones) are secreted by the adrenal medulla into the 
bloodstream and by sympathetic neurons in response to low blood glucose 
levels. Like glucagon, they stimulate the mobilization of glycogen and 
triacylglycerols by triggering the production of cyclic AMP (cAMP). 

When  adrenaline (or glucagon) binds its receptor (beta-adrenergic receptors or 
glucagon receptors), it activates the enzyme responsible for the formation 
of cAMP. cAMP in turn, activates an enzyme called protein kinase A, which 
phosphorylates other proteins (that is, covalently attaches a phosphate 
group to certain amino acid residues in specific proteins). 

Phosphorylation alters the enzymatic activity of these enzymes. In our case, the end result 
is the activation of glycogen phosphorylase which causes the breakdown of 
glycogen and simultaneously the inhibition of glycogen synthase which is 
responsible for the synthesis of glycogen. 

Adrenaline and noradrenaline differ from glucagon in that their glycogenolytic effect is greater in 
muscle than in liver. They also inhibit the uptake of glucose by muscle. 
Instead, fatty acids released from adipose tissue are used as fuel. 
Adrenaline also stimulates the secretion of glucagon and inhibits the 
secretion of insulin. Thus, catecholamines such as adrenaline and 
noradrenaline increase the amount of glucose released into the blood by 
the liver and decrease the utilization of glucose by muscle.

Hope this helps,


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