Distribution and function of angiotensin II receptors in mouse spermatozoa

Previous work indicates that angiotensin II (AngII) stimulates sperm motility and acrosomal exocytosis. Here we determined the distribution of AngII receptors on mouse sperm by immunocytochemistry and used Ca2+ probe photometry to examine their coupling to sperm regulatory pathways. We found both AT1 and AT2 receptors localized on the acrosomal region of the sperm head. The AT1 receptor, but not the AT2 receptor, is found also on the principal piece of the sperm tail. Local perfusion of motile but nonprogressive sperm with 0.1-1 microM of AngII evokes a rapid, substantial rise in intracellular [Ca2+]. This response is blocked by losartan, a specific antagonist of the AT1 receptor. These results indicate that sperm possess functional AT1 receptors that are distributed to sites that may allow selective control of motility and exocytosis. They also suggest that the AT2 receptors detected by immunoreactivity are either nonfunctional or are not coupled to Ca(2+)-mediated signalling mechanisms.