The expression of the placental anticoagulant protein, annexin V, by villous trophoblasts: Immunolocalization and in vitro regulation

G. Krikun, C. J. Lockwood, X. X. Wu, X. D. Zhou, S. Guller, C. Calandri, A. Guha, Y. Nemerson, J. H. Rand

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Abstract

We evaluated the histological and ultrastructural localization of the potent anticoagulant protein, annexin V, at the light and electron microscopic levels, using immunohistochemistry and an immunogold method. Annexin V was found to localize to the microvillar surface of the villous syncytiotrophoblasts. Isolated villous-derived trophoblasts were then utilized to evaluate the expression of annexin V protein mRNA in response to syncytialization in vitro, as well as to exposure to adenylate cyclase and protein kinase C agonists. Levels of immunoreactive annexin V released into the conditioned media and associated with cell protein were assessed by ELISA while levels of annexin V mRNA were evaluated by Northern analysis. No significant change in either media or cell-associated annexin V concentrations were detected over time in culture or in response to 1.5 mm 8-bromo-cyclic-adenosine-monophosphate (8-b-cAMP) or 0.15 nm phorbol ester myristic acid (PMA). These results indicate that annexin V is ideally positioned to inhibit intervillous thrombosis and maintain the fluidity of the intervillous circulation. Moreover, the absence of trophoblast annexin V regulation by intracellular second messenger regulators suggests that this crucial placental anticoagulant factor is constitutively produced.

Original languageEnglish
Pages (from-to)601-612
Number of pages12
JournalPlacenta
Volume15
Issue number6
DOIs
StatePublished - 1994

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