Fig. 2.

SLC4A11 mediates osmotic (independent of Na⁺) and electroneutral water movement in oocytes. A and B: oocytes (injected with cRNA-encoding N-terminally HA-epitope tagged SLC4A11 or AQP1 cRNA) were perfused with 220 mosM/kg isotonic oocyte ND96 medium (white bar), followed by 44 mosM/kg hypotonic solution (black bar). Perfusions proceeded in the absence (B) (replaced by choline chloride) or presence (A) of 96 mM NaCl. C: oocyte volume was calculated from images captured digitally every 15 s. Rate of volume change was represented by calculating the slope of initial swelling after switching to hypotonic solution. D: whole cell current was measured, with a single-barreled microelectrode, in oocytes injected with SLC4A11 cRNA or native oocytes. Oocytes were perfused with oocyte Ringer's solution (OR 7.4, white bar), 220 mosM/kg solution (isotonic, black bar), and 44 mosM/kg solution (hypotonic, white bar). E: SLC4A11 mediated membrane current, induced by switching from isotonic to hypotonic medium was determined for oocytes, during the first switch to hypo-osmotic medium. Error bars represent means ± SE (n = 7–10); *significant difference from H₂O-injected oocytes; #significant difference from SLC4A11-injected oocytes (P < 0.05); n.s., not significant.