title: Regulation of intracellular pH in hamster preimplantation embryos by the sodium hydrogen (Na+/H+) antiporter.
abstract: This study was an investigation of the mechanisms for the regulation of intracellular pH (pHi) by hamster preimplantation embryos. The resting pH values of hamster embryos were similar at the 1-cell (7. 19 +/- 0.34), 2-cell (7.21 +/- 0.21), and 8-cell (7.22 +/- 0.41) stages. Cleavage-stage hamster embryos alleviated intracellular acidosis by activity of the Na+/H+ antiporter. The rate of recovery from acidosis was similar for embryos at 1-cell, 2-cell, and 8-cell stages. When Na+/H+ antiporter activity was inhibited by either incubation in Na+-free medium or the presence of an inhibitor, pHi was unable to recover to initial levels. Instead, pHi remained acidic. The Na+/H+ antiporter was also found to contribute to baseline pH regulation, as incubation in Na+-free medium resulted in an immediate intracellular acidification. The set point for Na+/H+ antiporter was pH 7.14. There was no evidence at any developmental stage for activity of either Na+-dependent HCO3-/Cl- exchanger or H+-ATPase in the regulation of pHi. Inhibition of the Na+/H+ antiporter by an amiloride derivative significantly reduced the ability of 2-cell embryos to develop in culture when challenged with acidosis, indicating that the Na+/H+ antiporter is an essential regulator of pHi.
authors.affiliation: Department of Animal Health and Biomedical Sciences, University of Wisconsin, Madison, Wisconsin 53706, USA. lane@ahabs.wisc.edu
authors.forename: M
authors.initials: M
authors.lastname: Lane
authors.forename: J M
authors.initials: JM
authors.lastname: Baltz
authors.forename: B D
authors.initials: BD
authors.lastname: Bavister
mesh_terms: D000136:Acid-Base Equilibrium / Q000502:physiology*; D000138:Acidosis; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D017920:Antiporters / Q000502:physiology; D027963:Chloride-Bicarbonate Antiporters; D002970:Cleavage Stage, Ovum; D006224:Cricetinae; D003470:Culture Media; D046508:Culture Techniques; D004622:Embryo, Mammalian / Q000502:physiology*; D047108:Embryonic Development; D005260:Female; D006863:Hydrogen-Ion Concentration; D008647:Mesocricetus; D011247:Pregnancy; D006180:Proton-Translocating ATPases / Q000502:physiology; D012964:Sodium / Q000008:administration & dosage / Q000494:pharmacology; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000502:physiology*
chemical_list: D017920:Antiporters; D027963:Chloride-Bicarbonate Antiporters; D003470:Culture Media; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; D012964:Sodium; D006180:Proton-Translocating ATPases; C039614:ethylisopropylamiloride