Sc. So et al., Functional expression of sperm angiotensin II type I receptor in Xenopus oocyte: modulation of a sperm Ca2+-activated K+ channel, BBA-BIOMEMB, 1415(1), 1998, pp. 261-265
In addition to Ca2+ and K+ fluxes, angiotensin II (Ang II) has been shown t
o influence sperm motility. The present study investigated the involvement
of angiotensin II type 1 receptor (ATI) 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
mu M was found to potentiate the ionomycin-induced current, previously demo
nstrated to be mediated by a 'Maxi' Ca2+-activated K+ channel. However, at
higher concentration, 20 mu M, Ang II was found to suppress the ionomycin-i
nduced current. Both potentiating and inhibitory effects of Ang II were blo
cked by losartan, a specific antagonist of AT(1) receptors. Immunohistochem
ical studies further confirmed the presence of AT(1) receptors in spermatog
enic cells while expression of AT(1) receptor mRNA was demonstrated by RT-P
CR. These results suggest that Ang II may influence sperm motility as well
as other sperm function by acting on AT(1) receptors, and exerting potentia
ting and inhibitory effects on the Ca2+-activated K+ channels. (C) 1998 Els
evier Science B.V. All rights reserved.