Formation of catecholamines

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 and epinephrine.

·              Tyrosine 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.

·              DOPA is next decarboxylated to dopamine by a decarboxylase in the presence of pyridoxal phosphate.

·              Next dopamine is oxidised to yield norepinephrine. The reaction is catalysed by dopamine hydroxylase and ascorbic acid.

·              Methylation of norepinephrine in the medulla gives rise to epinephrine. The methyl group is derived from S-adenosyl methionine.