INCREASED CONTENT OF ANNEXIN-II (P36) AND P11 IN HUMAN PLACENTA BRUSH-BORDER MEMBRANE-VESICLES DURING SYNCYTIOTROPHOBLAST MATURATION AND DIFFERENTIATION

Annexins are a group of proteins abundant in placental membranes a her e they may play diverse functional roles. Annexins are expressed in hi gh levels in mature placenta but little is known about their presence at very early stages of gestation and later. We used the model of brus h-border membrane vesicles (BBMV) at different stages of gestation to assess precise localization of some of these proteins in syncytiotroph oblast apical membrane and to determine their appearance along the mat uration process of placenta. Here rue describe annexins type I, II, IV , V and VI which are present all along gestation in BBMV. Annexin II ( p36) is present with the S100 like calcium-binding protein p11 in BBMV , where they can constitute heterotetrameric forms of annexin II linke d to cytoskeleton structures. No variation of annexins I, IV and VI co ntent was observed in BBMV along pregnancy. Annexin V undergoes signif icant decrease after 12th week, which could be related to local antico agulant activity. Levels of annexin II and p11 increased progressively during gestation suggesting that heterotetrameric forms of annexin II play a role in the differentiation process of placenta and in functio n of the mature microvilli. (C) 1996 W. B. Saunders Company Ltd