title: Functional expression of sperm angiotensin II type I receptor in Xenopus oocyte: modulation of a sperm Ca2+-activated K+ channel.
abstract: In addition to Ca2+ and K+ fluxes, angiotensin II (Ang II) has been shown to influence sperm motility. The present study investigated the involvement of angiotensin II type 1 receptor (AT1) in mediating the modulatory effect of Ang II on a sperm Ca2+-activated K+ channel expressed in Xenopus oocytes injected with RNAs of spermatogenic cells. Ang II at a concentration of 1 microM was found to potentiate the ionomycin-induced current, previously demonstrated to be mediated by a 'Maxi' Ca2+-activated K+ channel. However, at higher concentration, 20 microM, Ang II was found to suppress the ionomycin-induced current. Both potentiating and inhibitory effects of Ang II were blocked by losartan, a specific antagonist of AT1 receptors. Immunohistochemical studies further confirmed the presence of AT1 receptors in spermatogenic cells while expression of AT1 receptor mRNA was demonstrated by RT-PCR. These results suggest that Ang II may influence sperm motility as well as other sperm function by acting on AT1 receptors, and exerting potentiating and inhibitory effects on the Ca2+-activated K+ channels.
authors.affiliation: Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors.forename: S C
authors.initials: SC
authors.lastname: So
authors.forename: W L
authors.initials: WL
authors.lastname: Wu
authors.forename: J
authors.initials: J
authors.lastname: Grima
authors.forename: P S
authors.initials: PS
authors.lastname: Leung
authors.forename: Y W
authors.initials: YW
authors.lastname: Chung
authors.forename: C Y
authors.initials: CY
authors.lastname: Cheng
authors.forename: P Y
authors.initials: PY
authors.lastname: Wong
authors.forename: Y C
authors.initials: YC
authors.lastname: Yan
authors.forename: H C
authors.initials: HC
authors.lastname: Chan
mesh_terms: D000804:Angiotensin II / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015640:Ion Channel Gating; D008297:Male; D009865:Oocytes / Q000378:metabolism; D015221:Potassium Channels / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011945:Receptors, Angiotensin / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013094:Spermatozoa / Q000378:metabolism*; D014981:Xenopus
chemical_list: D015221:Potassium Channels; D011945:Receptors, Angiotensin; D000804:Angiotensin II; D002118:Calcium