Page 197 - The Miracle of Hormones

A Wonderful Messenger:
Nitric Oxide

As you can see
in this picture,
blood vessels
can be stimulat-
ed to dilate and
constrict.

chemical products of this microscopic factory, nitric oxide messenger
molecules, are also just one millionth of a meter in size. To help us imag-
ine this measurement, the magnification required to see a NO molecule
as grape-sized with the naked eye would magnify a tennis ball to the
same size as the world. 80

The Short Life Story of the Messenger NO

Every nitric oxide molecule lasts about 10 seconds. It is designed to
communicate its message within this short time to the relevant recipients
and do this perfectly without fail. The messenger NO molecules secreted
by the endothelium cells are dispersed with great speed in every direc-
tion. Those which are directed towards the smooth muscle cells enter the
membrane of these cells. The smooth muscle cell membrane acts as a
selector giving entry to the NO it recognizes. Without wasting any time,

the NO molecule that enters the smooth muscle cells finds a special en-
zyme called GC and communicates its vitally important message. As a
result, a series of complex chemical reactions occur within the cell.
What we have called a messenger is a molecule, 0.000000001 meter

195