Viagra, the most famous drug for erectile dysfunction in men, stimulates the growth of sheep fetuses, researchers in the state of Texas have shown. For an article on a discovery that may help treat fetal developmental delay in livestock and in humans, see the Journal of Nutrition.
The latest research was inspired by jokes about Viagra that two Texas AgriLife Research scientists – Dr. Guoyao Wu and Dr. Tom Spencer – chatted with each other in 2003. We joked that many men are now using Viagra, but that they may need it also women. A week later, we saw an announcement that the drug’s manufacturer, Pfizer Inc., was awaiting proposals for research using the drug, Wu recalls.
Researchers submitted their project that tested Viagra’s effects on fetal development in pregnant sheep (these animals could be an excellent model for studying the physiology of human pregnancy). The company agreed to their proposal and the work started.
First, about 60 females were fertilized by rams. Some of them were well fed and some received only half of the daily nutrient requirements. From the 28th day of pregnancy, some females were injected subcutaneously with Viagra at two different concentrations, others received a placebo.
On day 115 of pregnancy, which in sheep has an average duration of 5 months, the scientists completed the experiment and collected tissue samples from females, fetuses and fragments of placenta for research.
It turned out that Viagra increased the content of essential amino acids and polyamines in the amniotic waters and tissues of fetuses from malnourished and well-fed sheep. As a result, fetuses whose mothers received the drug weighed more than those of placebo-treated females, although those in the malnourished group were generally smaller. The effects of the drug were directly proportional to its dose.
The researchers explain that Viagra, or sildenafil citrate, works by relaxing the smooth muscles of blood vessels and improving blood flow to many organs, including the uterus. In pregnant mammals, the drug may increase the transport of nutrients from the mother’s body to the fetus by improving the blood supply to the uterus and placenta, explains Dr. Wu.
Importantly, the drug did not affect the body weight of the mothers and their general condition, nor did it cause changes in the liver.
According to the authors of the study, these studies indicate that Viagra stimulation of blood circulation in the uterus and placenta may be an effective and safe strategy for pregnant women to deal with the problem of slowing fetal growth in farm animals, as well as in humans.
Researchers recall that 5 to 10 percent of the world’s population babies are born underweight.
In the future, the team of Dr. Wu plans to extend the experiments to other mammals such as pigs, cows and humans. (PAP)