Synthesis and Storage

Virtually all of the histamine found in individual organs and tissues is synthesized locally and stored in subcellu-lar secretory granules. Within the tissues, the mast cells are the principal sites of storage; in the blood, the ba-

sophils serve this function. Histamine is also present in neurons of the CNS, where it acts as a neurotransmitter.

Histamine is synthesized from the amino acid histi-dine by an action of the enzyme histidine decarboxylase (Fig. 38.1). Following synthesis, histamine is either rapidly inactivated or stored in the secretory granules of mast cells and basophils as an inactive complex with proteases and heparin sulfate or chondroitin sulfate.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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