Adrenaline
On Adrenaline
Many of us know adrenaline from the “fight or flight” response, but how does it actually work? Who discovered it? This blog serves to spread some information on the incredible hormone adrenaline.
The Discovery of Adrenaline
If you Google what the first hormone discovered was, Google will tell you it was “secretin,” but this is actually wrong. The first hormone discovered came through an experiment involving adrenal gland extracts. In 1894, British physician George Oliver was measuring the effects of an “adrenal extract” on the blood pressure of sheep. Oliver noticed that when he injected the sheep with the extract, blood pressure would instantly increase. Further experimentation showed that this increase in blood pressure would be present even when the nerves were severed. He concluded that the adrenal medulla must secrete a chemical into the bloodstream that acted independently of the nervous system. A few years later, in 1901, Japanese chemist Jokichi Takamine successfully isolated this mystery chemical from thousands of adrenal gland extracts, which he dubbed adrenaline.
Adrenaline or Epinephrine?
Why then does adrenaline have another name, epinephrine? The redundancy comes from the fact that two research groups discovered the hormone independently, the aforementioned Takamine and American pharmacologist John Jacob Abel. Abel attempted a purification of the compound and named his isolate “epinephrine,” from the Greek epi- "upon" and nephros "kidney.” Following the publication of both groups’ work, academia had to make a decision on which name to use for this newly discovered hormone. The decision point came in 1901 when Parke, Davis & Co. trademarked Takamine’s adrenal extract as “Adrenalin,” without the ‘e.’ American academics didn’t want to use a brand name in their papers, so they opted for epinephrine. Conversely, the rest of the world opted for adrenaline, as the trademark was limited to the US.
How Does Adrenaline Work?
Upon times of imminent danger, your body’s autonomic nervous system allows you to respond appropriately and instantly. The autonomic nervous system innervates the adrenal medulla, which can cause it to release adrenaline into the bloodstream. In the bloodstream, adrenaline travels through until it reaches the appropriate cells. Adrenaline cannot bind to just any organ, it specifically binds to cells that express adrenergic receptors on their cell membranes. These can be muscle cells, heart cells, intestinal cells, and others. Once bound, binding of adrenaline to adrenergic receptors causes changes in the cell like protein expression, ion flux, etc. These changes lead to an increased ability for the body to mobilize; energy is directed away from “rest and digest” functions like digestion, and towards “fight or flight” functions like muscle flexion or mental alertness.
Disorders Involving Adrenaline
Interestingly enough, insufficient adrenaline production is not necessarily associated with any major endocrine disorder. This is because there are many hormones that have similar actions on the body; noradrenaline (norepinephrine) has very similar effects on the body, and therefore can compensate for the loss of adrenaline. Conversely, too much adrenaline production due to a tumour in the adrenal medulla has more adverse consequences; pheochromocytoma, a tumour in the adrenal medulla, is infamous for its non-specific symptoms.
On the cover: the structure of adrenaline/epinephrine.
