As previous studies have shown, ouabain has the potential to reduce fertility in men. By disrupting sodium and calcium ion movement, it curbs the generation of a protein necessary for fertility. The viability of ouabain as a contraceptive has been debated upon, however, due to its effects on the heart. Ouabain is a cardiac glycoside, or an organic compound that decreases the rate of heart contractions while simultaneously increasing the organ's output force. Mammals naturally produce ouabain as a means of regulating blood pressure, though it can be obtained from plant sources as well. Ouabain is sometimes prescribed as a treatment for low blood pressure and irregular heartbeats, meaning that high doses of this compound can result in heart damage.
This inspired the researchers to create an ouabain analog that was free of its cardiotoxic properties but maintained its fertility-inhibiting qualities. A feat, the researchers explained, that the ouabain derivative accomplished by interfering with sperm motility and hyperactivation. By impeding the sperm cells' ability to swim, this greatly diminishes their chances of fertilizing an egg. Moreover, these effects were stated to be reversible as only mature sperm cells were targeted. So ceasing treatment would result in sperm cells that regained their motility.
Rat experiments carried out by the researchers demonstrated the efficacy of the ouabain derivative. The sperm levels of the rats who'd been given the compound were normal. However, the researchers noted that the rats' sperm was significantly less mobile. Tests on human males have yet to be carried out, so it might still be a long time coming before ouabain-derived contraceptives hit the shelves of pharmacies.
That may be a good thing. The ouabain coating the arrowheads of African warriors has been shown to cause high blood pressure, twitching, convulsions, and cardiac arrest. Meanwhile, the ouabain utilized for medicinal purposes can only be administered at very low doses because of its side effects. As such, giving ouabain-containing contraceptives to men could put them at high risk of heart events. (Related: New birth control shots for men are causing depression, mood swings.)
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