「バイアグラ使用で精子損傷　不妊の可能性」
英医学博士が警鐘

2月25日9時31分配信 産経新聞

【ロンドン＝木村正人】
24日の英紙デーリー・テレグラフ（電子版）によると、
男性の勃起不全治療薬、米ファイザー社のバイアグラを使用すると、
精子の一部が損傷して不妊の原因になる可能性があることが
英クイーンズ・ユニバーシティ・ベルファストの
デイビッド・グレン博士の研究で分かった。

グレン博士の研究チームは
バイアグラの薄い溶液につけた精子と普通の精子を比較。
その結果、バイアグラ溶液の精子は活発に動くようになったが、
精子核を覆う袋状のアクロソームが損傷していた。

精子が卵子を覆う透明帯に結合すると、
アクロソームの膜が壊れ内部の酵素が放出され、
精子が透明帯を通過できる。
アクロソームが損傷すると、精子の透明帯通過率が下がり、
不妊の原因になりかねないという。

バイアグラを投与したマウスの受精率も通常より40％も低かった。

グレン博士は同紙に
「バイアグラを長期使用すると不妊の原因になる可能性がある。
不妊治療中のカップルが使用するのも事態を悪くしかねない」
と話している。

*Yahoo!の記事はこちら*




”バイアグラの薄い溶液につけた精子と普通の精子を比較”

という実験方法がちょっとおもしろい。
有効性があるのかどうかわからないけど、
どうなのでしょう？




ただ、

”バイアグラを投与したマウスの受精率も通常より40％も低かった”

は非常に気になる。



でも、この研究、
Pfizer社のバイアグラに限ったもの？

バイアグラ以外のED治療薬としては、

Bayerのレビトラ（Levitra：日本での承認は2004年6月）、
Lillyのシアリス（Cialis：日本での承認は2007年7月）

（→いずれも商品名）


等がありますが、そちらはどうなのでしょう？


成分のどの部分が精子損傷の原因になっているのか、
論文を読んでみたいと思いましたわ。



なんだか、この日本の記事だけ読むと、
Pfizerの名前が一人歩きしそうな気がしたのは、
私だけなのかなあ･･･。








−−−−

*BBCの記事はらちら*


Viagra use 'may damage fertility'

Men who take Viagra when they are hoping to start a family
could be affecting their fertility.
The finding, by Queen's University, Belfast,
also casts doubt on the use of the anti-impotence drug by IVF clinics.

The researchers will tell a British Fertility Society meeting that
the drug does enhance sperm movement.

However, it also seems to undermine the timing of a chemical process
needed to fertilise the egg.
This process, known as the acrosome reaction,
releases digestive enzymes that break down the egg's protective outer layer,
allowing the sperm to penetrate more easily.

Viagra seems to speed up the acrosome reaction,
so that by the time the sperm reaches the egg it has no digestive enzymes
left to penetrate the outer layer.
Sperm that have undergone this process are known as fully "reacted".

The researchers tested 45 samples of semen.
They found that up to 79% more sperm were fully "reacted"
in samples treated with Viagra.

The findings echo previous work on mice showing
that in the presence of Viagra significantly fewer eggs
are fertilised - and fewer of the resulting embryos continue to develop.



Recreational use

Researcher Dr Sheena Lewis said the acrosome reaction
involved the channelling of charged calcium atoms, or ions.

It would be a terrible shame if an unnecessarily alarmist headline
put people off using a treatment which may actually help them


Dr John Dean
This was known to influence numerous cellular mechanisms
- and could effect early embryonic development.

Dr Lewis said: "When Viagra came out in 1998
it was aimed at men with impotence problems,
primarily older men not interested in having children.
Now it has become a very popular drug for sexual enhancement.

"The message we want to get across is that caution
should be taken when using recreational drugs
if you are hoping to start a family."

Dr David Glenn, who also worked on the study, said:
"Nearly half of licensed fertility units in the UK
currently use Viagra to assist patient semen production.

"Our study raises questions about the drug's use in assisted reproduction."

Sheena Young, from the support group Infertility Network UK,
said it was important

that people who used Viagra recreationally were fully aware of its full effect.

"When Viagra was introduced it was never meant for this purpose."

Caution urged

However, Dr John Dean, secretary general of the European Society
for Sexual Medicine,

told BBC News Online that
it was difficult to draw firm conclusions from the study.

He said lab results often did not reflect
what happened in the human body,
and sperm was known to be highly sensitive
when removed from its natural environment.

"Childless couples - and the general population -
should be aware that in the five years
that Viagra has been around no overall detrimental effect on fertility
has been observed," he said.

"It would be a terrible shame if an unnecessarily alarmist headline
put people off using a treatment which may actually help them."







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