服用伟哥对男性生殖力有影响

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Men who take Viagra 'put their fertility at risk'
Robin McKie, science editor The Observer, Sunday February 24 2008 Article history · Contact us

Using Viagra may be damaging men's fertility, researchers have warned. Experiments suggest that the anti-impotence drug can harm sperm and may prevent some men from fathering families.

In particular, young men who use the drug recreationally could impair their ability to have families. And fertility clinics that prescribe Viagra to help men produce sperm for IVF treatments could be preventing some couples from conceiving.

'I think it is worrying that some IVF clinics are using Viagra in order to boost fertility results,' said Dr David Glenn, a consultant gynaecologist at Queen's University Belfast. 'Couples that go there for treatment are, by definition, already having problems getting pregnant. Giving male partners something that could make the problem worse is scarcely the right approach.'

Glenn's research, which is to be published in the journal Fertility and Sterility, is based on two sets of experiments. The first involved taking sperm samples from volunteers and then bathing them in weak solutions of Viagra. The aim was to produce a Viagra level equivalent to that found in the blood of a man who had taken a single 100-milligram tablet.

The researchers then compared the behaviour of the treated sperm with standard samples and found the drug had two principal effects. It made sperm more active but also it damaged its acrosome, a cap-like structure that contains enzymes that break down the membrane surrounding a woman's egg and allows sperm to fertilise it.

'Essentially the acrosome breaks open too early in sperm that has been exposed to Viagra. The sperm cannot get into the egg and so it is not fertilised,' said Glenn.

His team carried out similar experiments on animals and found that sperm from mice that had been given Viagra produced 40 per cent fewer embryosthan those on control pills. However, there was no evidence that baby mice produced by male mice on Viagra had been damaged in any way.

'There are two main concerns raised by these findings,' Glenn told The Observer. 'First, Viagra has become a widely used recreational drug. It is mixed with cocaine, for example, and is sold in clubs. Our work leaves open the possibility that there could be a cumulative effect from taking Viagra, however, which could pose serious fertility problems in later life.'

Glenn's work also suggests that the use of Viagra by IVF clinics could pose problems for many couples. Last week The Observer contacted a number of British IVF clinics to ask if they administered Viagra to men. Several said they did. Others, such as the clinic at University College Hospital in London, said did not because it had been found that Viagra could damage sperm.

'Couples going to clinics already have fertility problems. Viagra may simply be making those worse,' said Glenn.

英国研究人员发现，服用伟哥能损伤男性的生育能力，原因是伟哥损伤了顶体。顶体中含有多种酶，能保证精子顺利与卵子结合从二达到受精目的。该结论在小鼠身上获得证实。目前伟哥长期滥用对未来男性未来生育能力的影响还未知，需要进一步研究。

最近，英国女王大学妇科顾问David Glenn开展了一项研究。将志愿者提供的精子浸泡在稀释的伟哥溶液里，构建与服用100mg伟哥后人体内血浓度一样的体外环境。用药组与对照组比较后发现，伟哥虽然增加了精子活动力，但却损伤了顶体（顶体是一种包含能够溶解女性卵子外周膜的酶，从而让精子受精）。事实上，如果精子顶体过早暴露在伟哥环境中，那么精子在尚未到达卵子周围就已经失去生育能力了。研究人员也开展了类似的动物试验。使用伟哥小鼠的精子与对照组相比少产生40%的晶胚。但目前尚无证据表明通过使用伟哥受孕娩出的小鼠有生理缺陷。

这一研究结果提出了两个值得关注的问题。首先，伟哥已经变成应用广泛的娱乐性药物，如俱乐部中出售伟哥与可卡因混合的“兴奋剂”。但目前的研究遗留了这样一种可能性：长期服用伟哥的累积效应有可能造成以后的不育问题。其次，英国部分开展试管受精的诊所通常使用伟哥帮助男性产生精子。但由于伟哥对精子的损伤作用，这对于本来就已经存在生育问题的患者而言，无疑是是雪上加霜。