Principles of Biochemistry

9.1.4.2 Hormones of Adrenal Medulla

The adrenal medulla secretes the amine epinephrine (adrenaline) and norepinephrine (noradrenalin). They are closely related hormones, made and secreted by the medulla, or inner portion, of the adrenal glands, which are located just above the kidneys.

The target tissues of epinephrine are the liver and skeletal muscles, as well as the heart and vascular system. It gives a rapid physiologic response to emergencies such as cold, fatigue, shock etc. It increases blood pressure and BMR. Epinephrin increases cAMP by activating adenyl cyclase. cAMP stimulates phosphorylase which causes the breakdown of glycogen in the liver resulting in increased blood sugar. Noreinephrin is one fifth potent in this respect.