Fig. 3. An increase of pHi during oocyte maturation induced by Na⁺/H⁺ antiporters coupling to 1-MA signal transduction. (A) Representative traces of pHi before and after 1-MA treatments. Fluorescence ratios of BCECF-dextran were measured every 30 seconds using a single oocyte before and after 1-MA treatments. Symbols represent oocytes treated with 1 µM 1-MA in normal SW (open circles, n=40), or in zero-Na⁺ artificial SW (0 NaSW) (closed diamonds, n=25) containing 480 mM choline chloride, 55 mM MgCl₂, 10 mM CaCl₂, 5 mM KCl, 2.5 mM KHCO₃, pH 8.0 adjusted with KOH, or in normal SW with 0.6 mM EIPA (open diamonds, n=22). Open triangles represent oocytes in normal seawater without 1-MA treatment (n=11). (B) Representative traces of pHi after Gß (0.6 µM) microinjection. Gß purified from bovine brain was stored in 0.6% Na⁺ cholate, 100 mM NaCl, 20 mM Tris-HCl, pH 8.0, and microinjected as previously described (Chiba et al., 1993). Fluorescence ratios of a single oocyte before and after Gß microinjection were measured. Symbols represent oocytes microinjected with Gß in normal SW (open circles, n=22) or in zero-Na⁺ artificial SW (closed diamonds, n=6), or microinjected in normal SW with the buffer used for Gß (open triangles, n=8). (C) The fluorescence ratios of a single oocyte in artificial SW with (open diamonds, n=14) or without (open circles, n=40) 0.1 mM LY294002 were measured before and after 1-MA treatment.