1. The catecholamines epinephrine (Epi) and norepinephrine (Norepi) are synthesized in chromaffin cells in the adrenal medulla in response to acetylcholine (Ach) release from preganglionic neurons of the sympathetic nervous system. Catecholamine synthesis from the precursor L-tyrosine involves 4 enzymatic reactions that take place in the cytosol of chromaffin cells. These are (1) hydroxylation of tyrosine to 3,4-dihydroxyphenylalanine (L-dopa) by tyrosine hydroxylase (TH), (2) decarboxylation of L-dopa to dopamine by dopa decarboxylase, (3) hydroxylation of dopamine to norepinephrine by dopamine β-hydroxylase, and (4) methylation of norepinephrine to epinephrine by phenylethanolamine N-methyltransferase (PNMT). NE, norepinephrine.
Source: Chapter 6. Adrenal Gland, Endocrine Physiology, 4e
Citation: Molina PE. Endocrine Physiology, 4e; 2013 Available at: Accessed: November 01, 2017
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