Formation of catecholamines
The adrenal glands in the human adult are
situated close to the upper pole of the kidneys and average 45 x 26 x 6 mm in
size and weighs about 10g each. The adrenal gland is divided into two distinct
portions - the medulla and cortex.
Catecholamines are secreted from the medullary
portion of the adrenal gland
These two hormones, belonging to the
catecholamine class of organic compounds, have potent biological activity in
both metabolic and physiologic regulations. Epinephrine regulates carbohydrate
metabolism, it has the effect of causing liver and muscle glycogenolysis,
hyperglycemia and glucosuria. The hormone causes increased oxygen consumption,
its effect being more rapid from that of thyroxine. Nor epinephrine causes
increase in blood pressure by causing an increase in peripheral resistance. The
hormone has, however, little effect on carbohydrate metabolism.
Tyrosine gets converted to form norepinephrine
is first hydroxylated to 3,4-dihydroxy phenylalanine (DOPA) by a
specificenzyme. DOPA is an intermediate which is common to the synthesis of
both epinephrine and melanin.
is next decarboxylated to dopamine by a decarboxylase in the presence of
dopamine is oxidised to yield norepinephrine. The reaction is catalysed by
dopamine hydroxylase and ascorbic acid.
of norepinephrine in the medulla gives rise to epinephrine. The methyl group is
derived from S-adenosyl methionine.