Vas deferens gene may help male infertility

Some progress has been made in the study of the potential applications of a non-hormonal male contraceptive pill. Somewhat ironically, the same technique may also have an effect on the treatment of some forms of male infertility. A letter published in Nature has detailed a scientific study on the gene which encodes for a receptor known as P2X(1).

This receptor is prominent in the smooth-muscle cells of the vas deferens - the ducts that carry sperm from the testicles before ejaculation - and is partly responsible for nerve stimulation of the muscles in the ducts that contract to aid sperm ejection. The study, so far only undertaken on mice, has shown that if the encoding gene is deleted, or 'knocked out', the number of sperm that reach the ejaculate is greatly reduced. Only 13.7% of female mice that mated with males with the 'knocked out' gene became pregnant, compared to 100% of those mated with males with the gene in operation. Thus the absence of the gene seems to fail to stimulate the P2X(1) receptor and, in turn, the receptor does not signal to the contracting muscles in the vas deferens. Deletion of the gene in humans would not provide a method of male contraception.

The P2X(1) receptors are found in numerous places throughout the body and deletion of the gene would therefore affect further body functions. However, the study has shown that if another way of disrupting the P2X(1) receptors in the vas deferens ducts was found, we may be on the way to development of a male contraceptive pill. The results also have implications for some kinds of male infertility treatment.

As the authors of the study have acknowledged, stimulation of the receptors may have an opposite effect and result in more sperm entering the ejaculate of men who have previously had low or no sperm counts.