Sodium/Potassium Adenosine Triphosphatase α- and β-Subunit and a-Subunit mRNA Levels during Mouse Embryo Development in Vitro1

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Abstract
Changes in sodium/potassium adenosine triphosphatase (Na+/K+ ATPase) and Na+/K+ ATPase mRNA content during preimplantation mouse embryo development were determined. Western blotting, using polyclonal antiserum against guinea pig Na+/K+ ATPase, was used to detect changes in Na+/K+ ATPase .alpha.- and .beta.-subunit content during mouse embryo development. Total RNA from mouse embryos was analyzed using Northern and slot blots hybridized with random-primer-labeled cDNA for Na+/K+ ATPase .alpha.-subunit from sheep kidney. Northern blots exhibited a single mRNA band (3.65 kb) in sheep and mouse kidneys and mouse embryos. Although Na+/K+ ATPase .alpha.-subunit mRNA content of mouse embryos increased 45-fold between Day 1 and Day 4 of development, Na+/K+ ATPase .alpha.-subunit content remained constant, and .beta.-subunit content increased 9-fold. The Na+/K+ ATPase .alpha.-subunit and .alpha.-subunit mRNA content did not increase in a similar manner. The results suggest that, in mouse embryos, blastocoel formation is not triggered by an increase in Na+/K+ ATPase .alpha.-subunit content. Changes in .beta.-solution content may be important in regulating Na+/K+ ATPase activity and blastocoel formation.