Chromaffin cell

Overview
Chromaffin cells are neuroendocrine cells found in the medulla of the adrenal gland (suprarenal gland - located above the kidneys) and in other ganglia of the sympathetic nervous system. They are derived from the embryonic neural crest.

In the fifth week of (human) fetal development, neuroblast cells migrate from the neural crest to form the sympathetic chain and preaortic ganglia. The cells migrate a second time to the adrenal medulla. Chromaffin cells also settle near the sympathetic ganglia, vagus nerve, paraganglia, and carotid arteries. In lower concentrations, extra-adrenal chromaffin cells also reside in the bladder wall, prostate, and behind the liver.

Function
Chromaffin cells of the adrenal medulla are innervated by the splanchnic nerve and secrete epinephrine, norepinephrine, and enkephalin into the bloodstream. As such, they play an important role in the fight-or-flight response. They are also referred to as granules and this is where the enzyme dopamine-hydroxylase catalyzes the conversion of dopamine to noradrenaline. Distinct N and E cell forms exist (also Na and A cells in British nomenclature - noradrenaline and adrenaline); the former produce norepinephrine, the latter arise out of N cells through interaction with glucocorticoids, and convert norepinephrine into epinephrine.

Nomenclature
These cells are so-named because they can be visualized by staining with chromium salts. Chromaffin salts oxidize and polymerize catecholamines to form a brown color, most strongly in the cells secreting noradrenaline.

(The enterochromaffin cells cells are so named because of their histological similarity to chromaffin cells (they also stain yellow when treated with chromium salts), but their function is quite different.)