Testosterone: A Potent Muscle Vasodilator

“Not many people understand what a pump is. It must be experienced to be understood. It is the greatest feeling that I get. I search for this pump because it means that that my muscles will grow when I get it. I get a pump when the blood is running into my muscles. They become really tight with blood. Like the skin is going to explode any minute. It’s like someone putting air in my muscles. It blows up. It feels fantastic.”
-Arnold Schwarzenegger

If bodybuilding had an official mascot for the sport it would have to be the fugu fish. The fugu fish gets its name from its ability to expand its body by two to three times it’s normal size when it becomes stressed. The fugu fish is also called the "pumper fish" or “puffer fish” because it inflates in times of stress. Just like the “puffer fish” when bodybuilder’s are training they get “pumped up.” Bodybuilders live for the pump; it may be because a good muscle pump causes a temporary increase in muscle size and feelings of euphoria. The pump felt so good that Arnold compared having a good muscle pump to having sex. He said, “The muscle pump is as satisfying to me as, uh, coming is, you know? As, ah, having sex with a woman and coming. And so can you believe how much I am in heaven? I am like, uh, getting the feeling of coming in a gym, I’m getting the feeling of coming at home, I’m getting the feeling of coming backstage when I pump up, when I pose in front of 5,000 people, I get the same feeling, so I am coming day and night. I mean, it’s terrific. Right? So you know, I am in heaven." The media for years has associated getting “pumped up” with bodybuilding; for years everyone used to laugh at Hans and Franz on Saturday Night Live because they were there to, “Pump You Up!” Nitric Oxide seems to be stealing all the press lately for getting bodybuilders pumped up but there are other key signaling agents that increase blood flow and cause vasodilation. The blood during resistance exercise pumps through a system of tubes called blood vessels. These blood vessels are lined with endothelial cells that secrete Nitric Oxide and contribute to having a good pump. Nitric Oxide opens blood vessels and helps to stimulate the flow of blood. Bodybuilders should also understand that in addition to Nitric Oxide, testosterone is also a potent muscle vasodilator.

Testosterone: A Tonic for the Heart

Testosterone’s action as a vasodilator has become a recent topic of interest to cardiologists. For many years, testosterone has been contraindicated for heart disease, but testosterone may be a natural tonic for the heart. Contrary to the popular notion that testosterone is bad for the heart, clinical studies have consistently report that testosterone therapy, whether administered chronically or acutely is associated with improvements in blood flow in men with coronary artery disease1,2,3. Recent studies have reported that blood testosterone concentrations are consistently lower in men with cardiovascular disease23. In animals, castration promotes arteriosclerosis while testosterone replacement therapy reduces it24. Testosterone causes direct vasodilation of blood vessels which might protect against cardiovascular disease, possibly by vasodilating blood vessels and reducing blood pressure.

Get your “SWOLE ON” with Testosterone.

Testosterone causes vasodilation in humans but also in animal studies of rabbit’s, dog’s, pig’s, and rat’s have all documented testosterone induced coronary vasodilation15. Contrary too many doctor’s thinking that testosterone is toxic to the heart, testosterone actually improves cardiac function. In one study, doctors infused testosterone directly into the right coronary artery of men with cardiovascular disease and found that testosterone increased the diameter of the artery, but there was also an increase in blood flow5. So what about when you are pumping up in the gym? It’s no coincidence that having high testosterone is going to lead to greater muscle pumps. When a researcher wants to measure vascular reactivity which is important for getting a good pump they measuring brachial artery dilation which a great way of measuring endothelial function. Researchers measured brachial artery dilation (the brachial artery runs from the shoulder down to the elbow) in response to high dose testosterone infusions. Compared with the placebo, high-dose testosterone caused a significant vasodilation of the brachial artery and enhanced blood flow. Testosterone interacts directly with androgen receptors; however testosterone mediated changes in blood flow is not mediated by the androgen receptor.

Testosterone causes Vasodilation Independently of the Androgen Receptor.

Before researchers can experiment on humans, they usually test their research ideas in lab cultures or test tubes. When researchers first experimented with the idea of testosterone being a vasodilator they used isolated blood vessels and infused testosterone into them, to the researchers surprise their was a direct vasodilator response of testosterone on the blood vessels11. Testosterone induces direct vasodilation in muscles, which is not mediated by the androgen receptor9. In that study, researchers administered a testosterone receptor blocker (antagonist) along with testosterone but found that testosterone induced vasodilation even though the androgen receptor was being blocked; this suggests that testosterone has direct vasodilating effects on vascular walls9. Testosterone produces a dose dependent effect on vasodilation8 (the more testosterone administered the greater the vasodilation.) It should also be mentioned that most of the studies used “free testosterone” analogs to produce the vasodilation in muscle because testosterone is highly bound to sex-hormone binding globulin. So the science minded reader knows that testosterone can convert to estrogen, could it be one of the metabolites of testosterone?

Testosterone Not Estrogen Causes Vasodilation

Men have a greater risk of cardiovascular disease than women, this gender difference in thought to be due to the cardioprotective effects of female hormones. Estrogen increases vasodilation, inhibits the response of blood vessels to injury, and inhibits the development of atherosclerosis in women. Estrogen-induced vasodilation occurs 5 to 20 minutes after estrogen has been administered and is not dependent on changes in gene expression. In men however, the administration of exogenous estrogen may actually increase the risk of death from coronary artery disease18. What’s interesting is that testosterone infusions cause vasodilation within minutes and the response is maximal within 20 minutes, whereas as classical interactions of the androgen receptor takes hours8; which means testosterone is having direct effects on the tissues. So what happens if you block the actions of estrogen? Surprisingly, inhibition of estrogen activity by an aromatase inhibitor or estrogen blocker has no effect on testosterone mediated dilation9, 10, 11. This suggests that testosterone has direct vasodilatory effect on muscle that is independent on estrogen. Unlike estrogen, testosterone has only a small effect on increasing Nitric Oxide production, as when researchers administer a Nitric Oxide inhibitor there is a decrease in testosterone induced vasodilation but nitric cxide does not fully block testosterone vasodilation12, 13, 14. These results suggest that testosterone’s actions on vasodilation are mediated only partly by Nitric Oxide.

Testosterone Works on Inhibition of Calcium channels

So if you are a bodybuilding/science geek and you want to know the exact physiological mechanisms for testosterone induced vasodilation then read on…Recent evidence suggest that testosterone causes vasodilation either through blocking calcium (Ca2-) channels. In fact, it has been proposed that physiological levels of testosterone act similar to the prescription Ca2- channel blocker nifedipine (a widely prescribed high blood pressure medication drug) used in the treatment of coronary artery disease and heart failure to reduce Ca2- concentration in smoothe muscle, therefore, promoting vasodilation of arteries and greater blood flow19. Calcium-channel blockers slow the rate at which calcium passes into the vessel walls. This relaxes the vessels. The relaxed vessels let blood flow more easily through them. Large scale studies have documented that testosterone levels are inversely related to resting blood pressure20, 21 (the higher the blood testosterone, the lower the blood pressure.) Would it be nice to have a doctor write you a script for testosterone because of your blood pressure was too high?

Other Supplements that can cause Vasodilation

In addition to testosterone have an effect on vasodilation and your Nitric Oxide supplements; there are a couple of other supplements that you can add that increase vasodilation. DHEA has not had a good track record for increasing strength, building muscle, or losing bodyfat but DHEA has been found to cause vasodilation16, 17; however the effects are less potent than testosterone. Fish oils are another great supplement that is a must for all bodybuilders. Fish oils, in addition to being anti-inflammatory, increasing insulin sensitivity, and reducing bodyfat are also vasodilators. For example, subject’s took10 capsules of Carlson’s Fish oils (~200 mg of DHA and ~300mg of EPA) for 10 weeks. The researchers found that 10 weeks of fish oils enhanced brachial artery dilation and blood flow during rhythmic muscle contractions25. Fish oils have been found to increase vasodilation by a couple of mechanisms: 1.) Fish oils increase prostaglandins PGI2 and PGI3 which are vasodilators26. 2.) Fish oils also increase Nitric Oxide production to enhance blood flow during exercise27, 28.

Key Points:

• Testosterone Increases vasodilation in a dose dependent fashion (the greater the testosterone, the greater the vasodilation)
• Testosterone causes direct vasodilation of muscle; independent of androgen receptor and estrogen.
• In large scale studies, testosterone is lower in men with heart disease and high blood pressure.
• Fish oils are great vasodilators and promote cardiovascular health.

References:
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