A marked animal-vegetal polarity in the localization of Na+ ,K+-ATPase activity and its down-regulation following progesterone-induced maturation

作者：Mohanty Basant Kumar^*; Gupta Brij L

来源：Molecular Reproduction and Development, 2012, 79(2): 138-160.

DOI：10.1002/mrd.22012

The stage-VI Xenopus oocyte has a very distinct animalvegetal 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, [3H]-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. 79:138160, 2012.

• 出版日期2012-2