A marked animal-vegetal polarity in the localization of Na(+),K(+) -ATPase activity and its down-regulation following progesterone-induced maturation.
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.
Department of Zoology, Cambridge University, Cambridge, UK. basant_colorado_edu@yahoo.com
Basant Kumar
BK
Mohanty
Brij L
BL
Gupta
D000818:Animals; D054239:Blastodisc / Q000378:metabolism / Q000648:ultrastructure; D002467:Cell Nucleus / Q000378:metabolism / Q000648:ultrastructure; D016764:Cell Polarity / Q000187:drug effects; D002970:Cleavage Stage, Ovum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D046529:Microscopy, Electron, Transmission; D008954:Models, Biological; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D009866:Oogenesis / Q000187:drug effects*; D011374:Progesterone / Q000494:pharmacology*; D011980:Receptors, Progesterone / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D014018:Tissue Distribution; D014982:Xenopus laevis
D011980:Receptors, Progesterone; D011374:Progesterone; D000254:Sodium-Potassium-Exchanging ATPase