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A marked animal–vegetal polarity in the localization of Na + ,K + ‐ATPase activity and its down‐regulation following progesterone‐induced maturation
Author(s) -
Mohanty Basant Kumar,
Gupta Brij L.
Publication year - 2012
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/mrd.22012
Subject(s) - germinal vesicle , biology , oocyte , polarity in embryogenesis , atpase , ouabain , cytochemistry , microbiology and biotechnology , medicine , enzyme , biochemistry , embryogenesis , embryo , chemistry , sodium , gastrulation , organic chemistry
Abstract The stage‐VI Xenopus oocyte has a very distinct animal–vegetal polarity with structural and functional asymmetry. In this study, we show the expression and distribution pattern of Na + ,K + ‐ATPase in stage‐VI oocytes, and its changes following progesterone‐induced maturation. Using enzyme‐specific electron microscopy phosphatase histochemistry, [ 3 H]‐ouabain autoradiography, and immunofluorescence cytochemistry at light microscopic level, we find that Na + ,K + ‐ATPase activity is mainly confined to the animal hemisphere. Electron microscopy histochemical results also suggest that polarized distribution of Na + ,K + ‐ATPase activity persists following progesterone‐induced maturation, and it becomes gradually more polarized towards the animal pole. The time course following progesterone‐induced maturation suggests that there is an initial up‐regulation and then gradual down‐regulation of Na + ,K + ‐ATPase activity leading to germinal vesicle breakdown (GVBD). By GVBD, the Na + ,K + ‐ATPase activity is completely down‐regulated due to endocytotic removal of pump molecules from the plasma membrane into the sub‐cortical region of the oocyte. This study provides the first direct evidence for a marked asymmetric localization of Na + ,K + ‐ATPase activity in any vertebrate oocyte. Here, we propose that such asymmetry in Na + ,K + ‐ATPase activity in stage‐VI oocytes, and their down‐regulation following progesterone‐induced maturation, is likely to have a role in the active state of the germinal vesicle in stage‐VI oocytes and chromosomal condensation after GVBD. Mol. Reprod. Dev. 79:138–160, 2012. © 2011 Wiley Periodicals, Inc.