Functional expression of sperm angiotensin II type I receptor in Xenopus oocyte: modulation of a sperm Ca2+-activated K+ channel.
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.
So
S C
SC
Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong.
Wu
W L
WL
Grima
J
J
Leung
P S
PS
Chung
Y W
YW
Cheng
C Y
CY
Wong
P Y
PY
Yan
Y C
YC
Chan
H C
HC
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
D015221:Potassium Channels; D011945:Receptors, Angiotensin; D000804:Angiotensin II; D002118:Calcium