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Hormonal Regulation of Fuel Metabolism:- Epinephrine Signals Impending Activity

المؤلف:  David L. Nelson، Michael M. Cox

المصدر:  Lehninger Principles of Biochemistry

الجزء والصفحة:  P908-909

2026-07-14

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Hormonal Regulation of Fuel Metabolism:- Epinephrine Signals Impending Activity

When an animal is confronted with a stressful situation that requires increased activity—fighting or fleeing, in the extreme case—neuronal signals from the brain trig ger the release of epinephrine and norepinephrine from the adrenal medulla. Both hormones dilate the respiratory passages to facilitate the uptake of O₂, increase the rate and strength of the heartbeat, and raise the blood pressure, thereby promoting the flow of O₂ and fuels to the tissues (Table 23–6). Epinephrine acts primarily on muscle, adipose, and liver tissues. It activates glycogen phosphorylase and in activates glycogen synthase by cAMP-dependent phos phorylation of the enzymes, thus stimulating the con version of liver glycogen to blood glucose, the fuel for anaerobic muscular work. Epinephrine also promotes the anaerobic breakdown of muscle glycogen by lactic acid fermentation, stimulating glycolytic ATP formation. The stimulation of glycolysis is accomplished by raising the concentration of fructose 2,6-bisphosphate, a potent allosteric activator of the key glycolytic enzyme phos phofructokinase-1. Epinephrine also stimulates fat mobilization in adipose tissue, activating (by cAMP-dependent phosphorylation) both perilipin and triacylglycerol lipase . Finally, epinephrine stimulates glucagon secretion and inhibits insulin secretion, reinforcing its effect of mobilizing fuels and inhibiting fuel storage.