My dog is broken!
By: Erica Choi and Christina Datuin
The Process of Erection
Nitric Oxide enters the cell (binds to
an intracellular receptor)
Guanylyl Cyclase becomes active
when Nitric Oxide binds to its
Binding of nitric oxide promotes the
synthesis of cGMP from GTP
cGMP binds to the regulatory
subunit, which makes an inactive
Activated PKG uses proteins and
ATP to create Phospho-proteins
that lower the concentration of Ca2+
This lowering of CA2+ causes the
smooth muscle cells in the penis to
relax, allowing blood to flow into
the penis, which then leads to
contracting aka erection!
Ginseng and Nitric
Ginseng helps produce more nitric
oxide, which is the signaling
molecule in this case. More nitric
oxide means that more guanylyl
cyclase is activated and more
cGMP is produced. Thus
activating more PKG, lowering
the CA2+ concentration, and
eventually leading to more
relaxation and then more of a
Viagra and PDE5
PDE5 is an inhibitor that prevents
the breakdown of cGMP by
phosphodiesterase. Since it binds at
the allosteric site opposed to the
catalytic site, it does not have to
compete with the signaling
molecules. SinceViagra enhances
erection it stops the PDE5 inhibitor
from working so that there will be
more cGMP, leading to more PKG,
less CA2+, more blood flow, and
then more relaxation and
What else could it be?
IfViagra and Ginseng don’t work, what could be the problem?
Well the IP3 receptor could be activated, therefore opening a
calcium channel which results in the release of Ca2+ into the
Phospholamban also regulates the Ca2+ channels in the
muscle cells. During relaxation phospholamban is
phosphorylated by kinase, removing the inhibition and
restoring low calcium levels in the cytoplasm.
MLC phosphatase prevents relaxation and controls the
components of the Ca2+ independent pathway.
PKG prevents the flow of Ca2+ into the cell, as does the K+
An increase of Ca2+ decreases the relaxation of the smooth
muscle cells in the penis, therefore preventing contraction. If
any of these proteins are malfunctioning, this could be the
cause of erectile dysfunction.