ISSN:
1432-0878
Keywords:
Key words: Placenta
;
Interplacentomal epithelium
;
Calbindin-D9k localisation
;
Calcium transport
;
Sheep (Clun
;
Welsh Mountain)
;
Cow (Friesian)
;
Goat (Saanen)
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract. In late pregnancy the sheep fetus requires 3 g of calcium per day, all of which must be transported across the trophoblast epithelium of the placenta. Such high levels of calcium transport across other epithelia are normally associated with the presence of calbindin-D9 or -28k. Our immunocytochemical results show that ovine, bovine and caprine interplacentomal trophoblast have high levels of calbindin-D9k, about eight to ten times more than in the placentomal region. The protein is detectable only in the uninucleate trophoblast cells in sheep and goat, the frequent binucleate cells show none. The calbindin-D9k is also present in the maternal glandular epithelium but not the surface epithelium of the uterus. The cellular distribution of the calbindin-D9k immunoreactivity suggests a soluble protein homogenously distributed through cytosol and nucleoplasm but absent from all organelles and intercellular spaces. In contrast, the uterine milk protein(s) are localised in Golgi cisternae and secretory vesicles in gland cells and in apical small endocytic vesicles and lysosomes in the uninucleate trophectodermal cells. The distribution of calbindin-D9k supports the concept that it mediates the high calcium flux by facilitated diffusion and not via any vesicular, membrane-bounded system.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004410050664
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