Ultrastructural cytochemistry of membrane-bound phosphatases in preimplantation mouse embryos

Vorbrodt, A.; Konwinski, M.; Solter, D.; Koprowski, H.

Developmental Biology 55(1): 117-134


ISSN/ISBN: 0012-1606
PMID: 188705
DOI: 10.1016/0012-1606(77)90324-4
Accession: 006857832

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The time of appearance and the ultrastructural localization of the enzyme activity of alkaline phosphatase (AlkPase), 5'-nucleotidase (5'Nuc), Mg2+-ATPase, transport ATPase, acyclic AMP phosphodiesterase (cAMP-PDase) and adenylate cyclase (AC) were investigated in unfertilized eggs and in mouse preimplantation embryos. Enzyme activity was associated only with the plasma membrane. AlkPase activity appeared only in limited areas of the plasma membrane of 1-cell embryos and increased in the 8-cell and morula stages. In blastocysts the enzyme activity was concentrated mainly in the trophoblast cells. 5'Nuc activity appeared 1st in 4- or 8-cell embryos and the highest activity was observed in trophoblast cells in the blastocyst and in plasma membrane between cells forming inner cell mass. Mg2+-activated ATPase activity was present in all embryos and in unfertilized egg plasma membrane. Transport (Na+K+)-ATPase appeared only in the closely apposed membranes of adjacent cells in morulae and blastocysts. A very low cAMP-PDase activity appeared between adjacent cells in 2-cell embryos, and the highest activity was observed on the outer surface of the plasma membrane of trophoblasts. AC was the only enzyme whose activity was located on the inner (cytoplasmic) side of the plasma membrane and appeared as early as the 1-cell stage embryo. The relation between the time of the appearance of enzyme activity and the preparation of embryos for implantation and upon embryonic proliferative activity is discussed.