Chromaffin cells are neuroendrocrine cells contained within the adrenal glands above each of the kidneys. Cells of this type are also located near the bladder wall, prostate gland, liver, carotid arteries, and the vagus nerve. They release chemicals called catecholamines into the bloodstream for immediate circulation throughout the entire body. When they are treated with chromium salts, they become a dark brown color that is easily visible under microscopic examination.
These cells get their name from the staining method they undergo to prepare them for microscopic examination. Chromium salts are used to stain the cells with color so that they can be seen. The catecholamines that are secreted by the chromaffin cells react most strongly with the chromium salts, turning the entire cell body a different color.
Chromaffin cells are first identifiable within the human body during the fifth week of embryo development. Shortly after development they migrate from the embryonic neural crest through the preaortic ganglia and then to the medulla of the adrenal glands. The sympathetic nervous system may also contain chromaffin cells in its ganglia.
A primary function of the chromaffin cells in the adrenal medulla is to release chemicals that can stimulate the body’s flight or fight response. Epinephrine and norepinephrine secreted by these cells bind to receptors in the brain, producing feelings of well-being, energy, and pain relief. Another effect of the epinephrine is an adrenaline burst that enables the body to complete physically taxing activities.
Chromaffin cells are also known to release a substance called enkephalins that cause feelings of euphoria. The feel-good effect of exercising can generally be attributed to the release of these opiate-like peptides. Being afraid, in pain, or physical exertion can trigger the chromaffin cells of the adrenal gland to produce more of these chemicals. Depending on the degree of stimulation, the amount of catecholamines released into the bloodstream can be greatly increased.
Heart muscle is immediately affected by the chemicals secreted by these cells. Blood is contracted through the heart with a much greater force than normal, resulting in a surge of freshly oxygenated blood into the body. As the rate of secretion slows, the heart rate will decrease until the normal rhythm has been restored.
The hepatic system is also strongly affected by the presence of the catecholamines in the blood stream. It speeds up glycogen processing in the liver, causing an increase in blood sugar levels. The liver is also prompted to accelerate the processing of toxic materials by the chromaffin cells.