Impotence Tied to Low Nitric Oxide

Los Angeles researchers have discovered a new clue to the cause of some forms of impotence, a sexual dysfunction that afflicts millions of adult men.

The researchers at the UCLA School of Medicine and Harbor-UCLA Medical Center suspect that impotence may sometimes be related to insufficient amounts of a chemical, nitric oxide, in the penis. Their findings are being published today in the New England Journal of Medicine.

The results may eventually lead to better methods of diagnosing impotence and improved therapies, said the research team, led by Dr. Jacob Rajfer.

The study was performed on pieces of penile tissue removed from 21 men when they had penile prostheses inserted because of impotence. The spongy tissue, known as the corpus cavernosum, contains smooth muscle that must relax in order for the penis to fill with blood and become erect during sexual arousal.

In the laboratory, the researchers stimulated the tissue with electrical fields. They studied the effects of various chemicals to determine whether they helped or hindered the relaxation of the muscle.

According to the scientists, the study confirmed a role for nitric oxide, a chemical that is known to relax smooth muscle.

Impotence is the inability of the adult male to achieve an erect penis, or less often, to ejaculate after having achieved an erection. It has many causes, including diabetes, prostate surgery and an insufficient blood supply to the penis. It is more common in older men.

It is estimated that about 10 million men in the United States have impotence or related problems.