The mechanism:
Biological systems rely on a complex set of primary and secondary messengers in order to regulate activity. In the reproductive system nitrous oxide, NO, is released locally from nerve endings in the endothelial cells of the erectile tissue(corpus carvenosum), when stimulated. Nitrous oxide is made with the aide of the enzyme NO synthase, which deaminates the amino acid L-arginine(Fig 1.),thus producing NO and citrulline. Fig 1. N0 mediated cGMP production
The NO then diffuses out of the cell in which it was synthesised, and into neighbouring cells. NO then acts with iron in the enzyme guanylyl cyclase to produce the intracellular mediator(second messenger) guanosine monophosphate Fig1) from guanosine triphosphate (GTP). This molecule cGMP is the vital component of the system. It acts as a vasodilator by relaxing smooth muscle in the blood vessels of the corpus cavernosum (see Fig 2.) Fig 2. The biological mechanism of sildenafil citrate
This leads to increased blood flow into the penis and hence an erection. In order to mediate this process a phosphodiesterase enzyme,drolyses the cGMP to an inactive form, GMP In healthy male this acts as a vital regulatory system. However, men suffering from erectile dysfunction (ED) may produce insufficient NO and hence insufficient amounts of cGMP, which are of course broken down by the PDE-5 enzyme to achieve an erection. Sildenafil Citrate binds with the active site of the PDE enzyme, thus preventing it from hydrolysing cGMP. This allows the produced cGMP to remain in its active form for longer and hence have a larger vasodilatory effect. Hence it does not cause an increase in the amount of vasodialator produced, but rather allows longer use of that which is. PDE receptors
The are nine different types of PDE receptor, found in different tissues of the body. However, the PDE-5 receptors are principally found in male erctile tissue and not in other parts of the body which explains the inactivity of sildenafil citrate as an antianginal drug(as coronary tissues use principally the pde-3 type receptors),seeDE-5 receptors are also found in platelets and various muscle tissues(Vascular, skeletal and visceral). The inhibition of these receptors by sildenafil helps to explain peripheral arterial venous dilation, inhibition of platelet thrombus, other side effects related to the PDE receptors include visionary distortion.(see, as PDE-6 receptors are found in the retina. Sildenafil has an affinity for this type of receptor, which is about 10 times smaller than that for PDE-5. Due to its mechanism of action sildenafil citrate will work on ED regardless of the cause as long as it involves lower levels of NO. However it is important to note that Viagra lengthens the life of cGMP, but does not directly produce it, hence cannot act as any sort of aphrodisiac Removal of Sildenafil from the body
Sildenafil is broken down in the liver by hepatic metabolism usingenzymes, mainly CYP450 3A4(major route),but also by CYP2C9(minor route) hepatic isoenzymes. The major product of metabolisation by these enzymes is N-desmethylated sildenafil, which is metabolised further. This metabolite has in itself has an affinity for the PDE receptors, about 40% of that of sildenafil. The metabolite is thus responsible for about 20% of sildenafils action. ow Does indeed Viagra Will work?
Viagra working method is reasonably very simple, the idea streets this PDE5, when this PDE5 is normally stopped up even more toxins this are responsible for this erection stay.That measures allows this circulation more desirable along with visits in the member much longer, of which allows sticking to this erection. Does Viagra Get the job done Not having Stimulation?
Many wonder, could Viagra work not having pleasure.The right formula is not any, simply because Viagra simply cannot work not having pleasure.You should be aroused to get Viagra to take the influence.With some product and don't acquire sexually excited, in that respect there is definately not any influence. How Fast Does indeed Viagra Get the job done?
This is normally a further usually query this adult men require.Properly is normally is dependent upon you.Consistent with trial offers, Viagra started to work within approximately fifteen min's.For most adult men, the idea will work within approximately half On what Viagra useful and also just how long, it depends on products you can this product, thisthat you're realigned along with about how certainly your whole body calls for the idea. Understanding Erections along with ED
If you intend to discover more desirable precisely how Viagra will work, its possible it would If your dude is normally sexually excited, this lack of feeling signs are generally dispatched within the human brain because of this member.Nerve signs cause several toxins to be published. Muscle tissues in the member are generally calm using these kind of toxins.When muscles within this member are generally calm, volumes with maintain are able to insert this member, next the idea cause cures telephone - Erectile.

Source: http://ayurvedamart.com/mech.pdf


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