Murine epididymal spermatozoa were dispersed in a medium of native osmolality and then transferred to a hypo-osmotic medium to mimic the physiological osmotic challenge, as encountered upon ejaculation into the female tract. The addition of quinine to block sperm K -channels for volume regulation resulted in a size increase of viable cells. Preincubation in 0.1 mM HgCl2, a standard aquaporin inhibitor, prevented such cell swelling. Addition of the K -ionophore valinomycin to quinine-swollen sperm reversed the swelling, but not after pretreatment of the swollen sperm by HgCl2. Aqp7, Aqp8, and Aqp9 mRNAs were identified in spermatozoa by RT-PCR, and the entire open reading frames were sequenced and compared with the GenBank database. Western blotting demonstrated specific protein signals for sperm AQP7 and AQP8 expression but probably not AQP9. The role of Hg2 -insensitive AQP7, if any, in sperm volume regulation was studied in transgenic mice. Spermatozoa from Aqp7−/− mice were the same size as wild-type sperm in basal conditions. Quinine-swollen volume, swelling reversal by valinomycin, and inhibition by Hg2 were also similar, indicating efficient water transport in the absence of AQP7. However, both water influx and efflux occurred faster in Aqp7−/− sperm than wild-type. This faster water movement in the knockout mouse spermatozoa was explainable by an upregulation of Aqp8 expression as revealed by quantitative PCR. Therefore, the Hg2 -sensitive AQP8, which was localized in elongated spermatids and spermatozoa, is a likely candidate for a water channel responsible for physiological sperm volume regulation crucial to in vivo fertilization.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 80 • No. 2