Dr. med. Dirk Manski

 You are here: Urology Textbook > Anatomy > Adrenal Glands

Adrenal Glands: Catecholamines

Biosynthesis of Catecholamines

The amino acid phenylalanine is the precursor of all catecholamines, they are synthesized via the following steps: tyrosine, dopa, dopamine, norepinephrine and epinephrine. The rate-limiting enzyme is tyrosine hydroxylase, which catalyzes the conversion of phenylalanine into tyrosine and dopa.

Effects of catecholamines

Adrenaline acts on alpha-1, beta-1 and beta-2 receptors. Noradrenaline acts mainly on alpha-1 receptors, rather than the beta-1 receptors. Dopamine acts in small doses on the dopamine receptor DA 1 and 2, in higher doses on alpha-1 receptors.

Metabolism of Catecholamines

The plasma half-life of epinephrine is around 20 s. The inactivation of adrenaline depends mainly on monoamine oxidase (MAO) and catecholamine-O-methyltransferase (COMT). The metabolic products are vanillylmandelic acid, metadrenaline (metanephrine), and normetadrenaline (normetanephrine); they are excreted via the urine. Furthermore, catecholamines are inactivated via re-uptake and re-used as neurotransmitters.

Index: 1–9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


Benninghoff 1993 BENNINGHOFF, A.: Makroskopische Anatomie, Embryologie und Histologie des Menschen.
15. Auflage.
München; Wien; Baltimore : Urban und Schwarzenberg, 1993

  Deutsche Version: Katecholamine der Nebennieren