"Heart failure patients may become noncompliant with their congestive heart failure (CHF) treatment if they feel it causes or aggravates their ED," Bocchi says. "However, our study suggests that treating the ED may make patients more motivated to take their medicines."

Sildenafil caused no harmful effects and improved exercise performance during treadmill exercise tests in 23 men with CHF (average age 50) and a history of ED, says Bocchi.

Sildenafil blocks the activity of the enzyme phosphodiesterase type 5 (PDE5), which is active in multiple tissues and cells. The effects of PDE5 inhibition include increased production of nitric oxide, which is associated with improved function of the heart and blood vessels.

The cardiovascular effects of sildenafil have created some concern that the drug might be harmful in men with CHF. But there's not enough data on the safety or potential harm of sildenafil in CHF patients.

Most of the men had moderate or severe heart failure, and each had been referred for treatment of ED. On separate days, the men underwent two exercise treadmill tests, which consisted of a six-minute walk and a maximal exercise test. About an hour before the first test, the men received either 50 milligrams of sildenafil or a placebo. On the second day, the men received the opposite treatment (sildenafil or placebo) before exercise.

Those treated with sildenafil had significantly lower blood pressure and heart rate and improvement in measures of oxygen consumption and carbon dioxide production compared with those on placebo. Total exercise time also increased significantly. A separate evaluation showed that treatment with sildenafil was associated with higher scores on a questionnaire related to erectile function.

"Frequently, CHF patients, and especially their wives, are afraid their spouses will have heart failure symptoms or even death during sexual activity," says Bocchi. "Our study shows that the benefits may outweigh harmful side effects of treatment with sildenafil. The successful treatment of ED in CHF could not only improve sexual relationships but overall quality and success of CHF treatment."

When Viagra was introduced several years ago, the drug's manufacturer warned of a number of visual side effects, including possible nerve damage to the eyes. But a UC Irvine College of Medicine study rules out some of these risks - even when the drug is taken in high doses.

Thanks to : Penis Pills

The study, to be published in the Jan. 10 issue of the scientific journal Cell, amends 20 years of scientific claims that cGMP acts to prevent platelet aggregation.

While platelet aggregation helps minimize the loss of blood when injury occurs, it can also lead to clotting that blocks a blood vessel - a life-threatening condition called thrombosis that can cause heart attack and stroke.

"Viagra, by itself, probably is not sufficient to cause a heart attack in healthy people, but our research suggests that it may present a risk for patients with preexisting conditions such as atherosclerosis," said Xiaoping Du, associate professor of pharmacology and the study's lead author.

Du said he and his coworkers had not set out to investigate the cause of fatalities in Viagra patients when they began their research about five years ago. Rather, as a basic research scientist, he was hoping to illuminate the highly complex series of molecular steps that control platelet aggregation.

Platelets are disk-shaped cells that freely circulate in the blood. When a blood vessel is injured, the platelets form sticky surfaces, adhering to one another and to the damaged area to plug the hole.

Using recombinant DNA techniques, the researchers forced standard laboratory cells to manufacture two proteins key to platelet aggregation: one that helps the platelets clump together and stick to the surface of broken blood vessels, and another that activates the first. The genetic manipulation enabled the researchers to isolate and study the molecules that trigger these proteins.

Du focused on PKG, or cGMP-dependent protein kinase.

"It was accepted knowledge that cGMP, by stimulating PKG-catalyzed reactions in platelets, inhibits their clumping," said Du. To his astonishment, he and his colleagues found otherwise.

"When we put PKG into the recombinant cells, we found that we actually made the cells more adherent," Du said.

The results were so surprising that the researchers wondered whether there was something special about the laboratory cells that made them react differently. But tests in mouse and human platelets yielded the same results. Moreover, platelets from mice incapable of manufacturing PKG failed to aggregate as well as platelets from normal mice.

Reconciling their findings with earlier scientific evidence that cGMP inhibits platelet aggregation, the UIC researchers believe that cGMP initially causes platelets to clump to seal a wound, but later reverses to stop an excessive buildup of cells that might block a blood vessel. If a person were at risk of thrombosis - if, for instance, a damaged blood vessel were already narrowed - even the initial accumulation of platelets could be sufficient to cause a problem.

Since Viagra is known to work by inhibiting an enzyme that breaks down cGMP, and hence raises its level, Du and his colleagues tested the drug on platelets taken from normal donors. Alone, Viagra did not promote platelet aggregation, but it did so in the presence of a small amount of other compounds typically present when a blood vessel is damaged. In fact, Viagra caused the cells to clump at concentrations well below those achieved in patients prescribed the drug for erectile dysfunction.

An estimated 16 million men worldwide have taken Viagra.

Cigarette smoking significantly increases the risk of erectile dysfunction, according to a study reported today at the American Heart Association's 43rd Annual Conference on Cardiovascular Disease Epidemiology and Prevention.

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These findings, presented to the American Urological Association, have implications for men who need reconstruction of the penis, and for men whose penis is intact but has suffered nerve damage - such as men who have undergone radical surgery for prostate cancer.

Although the body of the penis can be grown in the lab through tissue engineering using smooth muscle cells, the organ needs a working network of nerves in order to achieve erection and function sexually. This animal study, led by Anthony Atala, MD, director of Tissue Engineering at Children's Hospital Boston, showed that implantation of engineered tissue made of collagen can coax nerves to regenerate in the penis.

The investigators cut the cavernosal nerves - the two bundles of nerves innervating the penis - in 90 rats. At the injury site, they implanted either a graft of the rats' own nerves, or a graft made from collagen, a natural protein found in connective tissue. Some severed nerves were left untreated. The collagen grafts had been engineered to form a channel shape, similar to the natural sheath of a nerve, and follow-up studies three months later showed that the rats' own nerve cells had regenerated and infiltrated this "scaffolding" material. "We used the body's own healing abilities to create the tissue," explains Atala.

The degree of nerve regeneration with the collagen grafts equaled that of both normal, undamaged nerves, and the grafts consisting of the rats' own nerves. The severed nerves that were left untreated showed no signs of regeneration.

Atala's lab previously showed that the tissue making up the body of the penis can be successfully grown in the lab, and successfully used to reconstruct the penises of rabbits that had part of the organ surgically removed. This new study takes penile reconstruction a step further; showing that the nerves required for erectile function can be induced to grow through tissue engineering.

"Right now we can do partial penile repair, but in order to do complete replacements, we need to make sure all the parts are there, including the nerves," Atala said. "This research takes us one step closer." Future work will attempt to tissue-engineer a complete penis, growing the body of the organ and providing it with a functioning set of nerves.