The gamma-subunit of the Na-K-ATPase as a potential regulator of apical and basolateral Na+-pump isozymes during development of bovine pre-attachment embryos.
Expression and activity of the Na-K-ATPase within the basolateral membrane domains of the trophectoderm epithelium provide the driving force for accumulation of Na(+) and Cl(-) across the nascent epithelium, mediating fluid movement into the forming blastocoel. Within the trophectoderm of the bovine blastocyst, multiple isozymes of the Na-K-ATPase are expressed. Immunolocalization has demonstrated that the alpha1-isozyme localizes within the basolateral membrane, whereas the alpha 3-isozyme localizes to the apical cell margins. Gene-specific RT-PCR and wholemount indirect immunofluorescence confocal laser scanning microscopy were used to examine expression of the Na-K-ATPase gamma-subunit (a regulatory subunit of the Na-K-ATPase) throughout development of bovine preattachment embryos in vitro. Expression of mRNA transcripts for the gamma-subunit was detected throughout bovine pre-attachment development from the fertilized one-cell embryo to the blastocyst stage. A similar pattern of expression was also observed for gamma-subunit protein, and immunofluorescence was detected within the membranes of embryonic blastomeres at all stages of development. In contrast to the expression patterns observed for the alpha-subunits, gamma-subunit proteins were detected in both the basolateral and apical cell margins of the trophectoderm, and surrounding all cells of the inner cell mass. Co-localization studies demonstrated that gamma-subunit peptides are co-expressed with the alpha1-subunit in the basolateral domains of the trophectoderm. These results indicate a role for the gamma-subunit of the Na-K-ATPase in modulating Na(+)-pump activity in both apical and basolateral margins of the trophectoderm during formation and expansion of the bovine blastocyst, and adds a further level of complexity to Na(+)-pump regulation of cavitation.
Departments of Obstetrics and Gynaecology and Physiology, The University of Western Ontario, London, Ontario N6A 5C1, Canada.
L C
LC
Barcroft
S E
SE
Gill
A J
AJ
Watson
D000818:Animals; D001483:Base Sequence; D001755:Blastocyst / Q000201:enzymology / Q000378:metabolism*; D002417:Cattle / Q000378:metabolism*; D047108:Embryonic Development / Q000502:physiology*; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D015870:Gene Expression; D007527:Isoenzymes / Q000502:physiology; D008969:Molecular Sequence Data; D011247:Pregnancy; D012333:RNA, Messenger / Q000235:genetics; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic
D007527:Isoenzymes; D012333:RNA, Messenger; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase