Dr. med. Dirk Manski



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Adrenal Glands: Catecholamins

References: (Benninghoff, 1993).

Biosynthesis of Catecholamins

The amino acid phenylalanine is the precursor of all catecholamins, 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 catecholamins

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 the monoamine oxidase (MAO) and catecholamine-O-methyltransferase (COMT). The metabolic products are vanillylmandelic acid, metaadrenalin and metanoradrenalin; they are excreted via the urine. Furthermore, catecholamins 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



References

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