Apparent absence of Na+/H+ antiport activity in the two-cell mouse embryo.
We have used the pH-sensitive dye BCECF to investigate the regulation of intracellular pH (pHi) by two-cell stage mouse embryos in bicarbonate-free medium. There is no indication of a Na+/H+ antiport active in regulating pHi, as recovery from acid-loading was insensitive to amiloride, ethylisopropylamiloride, or the absence of extracellular Na+. Instead, protons appear to be in equilibrium across the plasma membrane, as indicated by the response of pHi to changes in external K+. The embryos have an intracellular buffering power in the normal range (25.3 mM/pH); their apparent permeability to protons is, however, very high (0.22 cm/sec).
Baltz
J M
JM
Laboratory of Human Reproduction and Reproductive Biology, Harvard Medical School, Boston, Massachusetts 02115.
Biggers
J D
JD
Lechene
C
C
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D001755:Blastocyst / Q000187:drug effects / Q000502:physiology*; D002352:Carrier Proteins / Q000378:metabolism*; D003470:Culture Media; D005260:Female; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D008433:Mathematics; D051379:Mice; D008815:Mice, Inbred Strains; D008954:Models, Biological; D009924:Organ Culture Techniques; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers
D002352:Carrier Proteins; D003470:Culture Media; D017923:Sodium-Hydrogen Exchangers; D012964:Sodium; D011188:Potassium