Viagra might have another role to play

• Texas AgriLife Research scientists have found that Viagra can be beneficial in promoting foetal growth in pregnant sheep.
• The findings could lead to future studies involving human pregnancies, leading to potential discoveries reducing the number of infants born as low birth-weight babies with reduced chances of survival and increased risks for adult onset of disease.
• Foetal development has been a focus of study in livestock species because small offspring do not do well after birth.
• Viagra (sildenafil citrate) was found by researchers to increase blood flow to the uterus and foetus in female sheep, supplying amino acids (a major fuel for foetal growth), as well as other essential nutrients.

Findings could have important implications for human health, agriculture

A joke among two Texas AgriLife Research scientists later turned into a fully-funded study found Viagra can aid foetal development in female sheep. Female sheep (ewes) are an agriculturally important species, which can serve as an excellent animal model for studying the physiology of human pregnancy, the researchers said.

Viagra (sildenafil citrate), which is used to treat male erectile dysfunction, enhanced blood flow in pregnant female sheep, helping send vital amino acids and other nutrients needed in foetal development. The study's results not only will assist with solving foetal development problems in other livestock, but possibly in humans, said Dr. Guoyao Wu, AgriLife Research animal nutritionist and Senior Faculty Fellow in the Department of Animal Science at Texas A&M University.

"Because 5% to 10% of infants are born as low birth-weight babies worldwide, and because foetal-growth retardation is also a significant problem in livestock species, our findings have important implications for both human health and animal agriculture," Wu said.

The findings appear in a recent edition of The Journal of Nutrition (www.nutrition.org).

Many a word, spoken in jest…

The study originated in 2003 after a chat between Wu and fellow AgriLife Research scientist Dr. Tom Spencer when they were working with pregnant ewes.

"We made a joke that many men are now using Viagra and that women may also have a need for it," Wu said. "Interestingly, one week later, we saw that Pfizer Inc. announced an international request for research proposals on Viagra."

The team submitted a proposal to Pfizer, using pregnant sheep as an animal model for evaluating Viagra's potential role in enhancing foetal growth. The research team would also evaluate both adequate or inadequate maternal intakes of nutrients from the diet, Wu said.

Pfizer selected the proposal and work began.

Viagra can enhance nutrient supply

"Viagra acts like nitric oxide to relax smooth muscle cells of blood vessels and, in turn, allow for increased uterine blood flow," Wu said.

The drug is a synthetic medicine that can be used to stimulate blood flow in humans and animals.

"For pregnant mammals, Viagra can enhance the supply of nutrients from the mother to the foetus via utero-placental blood flow," he said.

The study revealed Viagra increased the blood supply to the foetus in female sheep, supplying amino acids - a major fuel for foetal growth. Approximately 60 ewes were mated to rams at the Texas A&M University Sheep Centre. Pregnant females were randomly selected and treated with or without sildenafil citrate.

Plans are to extend research

Results of the study indicated long-term use of Viagra enhanced foetal weight in both "adequately fed and nutrient-restricted female sheep." Greater concentrations of amino acids and polyamines in foetal blood and placental fluids were found, leading the researchers to suggest that Viagra alters the trafficking of nutrients from the female sheep to the foetus.

It was also observed that Viagra did not affect changes in maternal weight, body condition score, maternal liver mass or muscle weight, Wu said.

"We were surprised that Viagra enhanced ovine foetal growth under the conditions of either adequate or inadequate maternal intakes of nutrients from the diet. The results of our study indicate that augmenting systemic blood flow may be a novel and effective strategy to prevent foetal growth retardation in humans and livestock species without affecting maternal health."

Wu said the team would like to extend its research into future studies involving other mammalian species, including pigs, cows and humans.

Source: Texas AgriLife Research and Texas A&M AgriLife Communications