Torpedo californica

Stewart N. Abramson sna at prophet.pharm.pitt.edu
Thu Feb 2 15:09:52 EST 1995


In article <3godti$c4i at ucunix.san.uc.edu>, naussjl at ucunix.san.uc.edu
(Jeffrey L Nauss) wrote:

> I have been reading recently about work on acetylcholinesterase.
> Often, I find that source for the protein is Torpedo californica.
> Could someone please briefly describe to this ignorant chemist what is
> Torpedo californica?  Why is this creature used so often to study
> acetylcholinesterase?

Torpedo are electric rays.  They are sort of flat, usually all black,
often swim near bottom and bury in sand.  Their elecric organs are made up
of lots of cells (electrocytes) that are designed to have one membrane
(one side of the cell) held at a low voltage potential while the other
membrane (other side of the cell) is depolarized.  The result is like a
battery.  Thus the electic organs can generate a charge that the ray uses
to stun its prey so that it can catch it and eat it.

In Torpedo, the depolarization of electrocytes is accomplished by release
of acetylcholine from nerve terminals.  The acetylcholine released from
the nerve terminals activates nicotinic acetylcholine receptors on the
electrocytes and sodium ions flow through the receptors causing
depolarization.  Acetylcholine is degraded by the enzyme
acetylcholinesterase.  Thus Torpedo electric organs are used as a source
of nicotinic receptors and acetylcholinesterase since they have these
proteins in much MUCH greater abundance than any other tissue.  They also
have Na+/K+ ATPase in great abundance, since something has to pump out the
sodium that flows into the electrocytes.

Hope that helps

Stewart Abramson

-- 
Stewart N. Abramson
Assistant Professor
Department of Pharmacology
University of Pittsburgh

sna at prophet.pharm.pitt.edu



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