Angiotensin II type 1 receptors were found in human sperm, but they were restricted to the specific regions of the tail (not the acrosomal region). Exposure to angiotensin II was found to stimulate motility. In contrast, an angiotensin II type 1 receptor antagonist/blocker (ARB) was found to inhibit angiotensis II type 1 stimulation of motility. In this particular study, angiotensin II receptors were not found on the anterior region of the sperm head overlying the acrosome. Hence, the authors concluded that, in [i]human[/i] sperm, the effect of angiotensin II was restricted to stimulating motility. There was no mention of its effect on the acrosome reaction (the release of enzymes that disolve the protein coat surrounding the egg) in human sperm.
Reference: J Endocrinol. 1995 Feb;144(2):369-78.
Type 1 angiotensin II receptors in rat and human sperm. Vinson GP, et al.
In a subsequent study of bovine (cow) sperm, angiotensin II receptors were found in both the sperm head and tail and angiotensin II had a stimulatory effect on both motility and the acrosome reaction. This effect was inhibited by Losartan, an ARB. This suggested that angiotensin may play a role in the induction of the acrosome reaction in bovine sperm.
Am J Physiol. 1998 Jul;275(1 Pt 1):E87-93.
Angiotensin II induces acrosomal exocytosis in bovine spermatozoa. Gur Y, et al.
In a similar study, angiotensin II was found to stimulate the acrosome reaction of equine (horse) sperm. THis was also inhibited by the ARB Losartan. The authors concluded that angiotensin II may play a role in the induction of the acrosome reaction.
J Reprod Fertil. 2000 Sep;120(1):135-42.
Effects of angiotensin II on the acrosome reaction in equine spermatozoa. Sabeur K, et al.
I am unaware of any scientific studies directly linking ARBs to the inhibition of the acrosome reaction in [i]human[/i] sperm. Although it is possible that angiotensin II receptor blockers may inhibit the acrosome reaction in human sperm, the direct evidence is just not there. It is important to recognize the dangers of making cross-species jumps. In reproduction, there are significant differences between species and what is found to be true in one specieis may not necessarily be true for another species.
It is not surprising that your RE was unaware of the angiotensin II receptor blocker studies on cow and horse sperm. It is difficult enough to keep up with human reproductive studies, let alone farm animals.
All this being said, I think you have a valid point. Patients should be more proactive in asking their physicians about the possible reproductive side effects of the medications they are on and REs need to be more aware of the negative effect of certain medfications on SPERM. Although ARBs are contra-indicated in pregnant women (they may cause birth defects), there is no mention of the potential side effects of ARBs on sperm function. And its not just ARBs. Reproductive toxicity studies are not required by pharmacuetical companies (in the US) before bringing a drug to market. There are some prescription medications that affect sperm funtion (i.e. ACE inhibitors), but you won't find that written in the product insert. Personally, I think the FDA should require more extensive reproductive studies before approving a drug. Yeah right. Like that's gonna happen.
Thanks for making your point.