OVINE AMNIOTIC AND ALLANTOIC EPITHELIA ACROSS GESTATION

Background: Extensive studies on the regulation of the volume and comp osition of amniotic and allantoic fluid in the sheep have suggested th at the amniotic and allantoic membranes must play an active role in th ese processes. Little is known of the functional morphology of the she ep amnion and allantois beyond the presence of an epithelium overlying connective tissue. Methods: The ovine amnion and allantois were chara cterized at a range of gestational ages (27-140 days of gestation, whe re term is 145-150 days) by electron microscopy (SEM and TEM) and the presence of transporting ATPases examined by use of immunohistochemist ry (Ca++-ATPase) and in situ hybridization (Na,K-ATPase), Results: Wit h increasing gestational age, the cell height of epithelium of the mem branes increased, as did the number of apical microvilli and the lengt h of zonulae occludentes. Epithelial cell cytoplasm increased in compl exity, and cell shape changed fr om flattened to cuboidal. Proliferati on of cells occurred until close to term. Immunoreactivity to Ca++-ATP ase was present in the basolateral membranes at all stages of gestatio n examined, but hybridization with the alpha and beta subunits of Na,K -ATPase was present only at or after 100 days of gestation. Conclusion s: The epithelia of the sheep amnion and allantois display characteris tics typical of transporting epithelia. As the epithelia mature, chang es related to increased capacity for salute and fluid transport regula tion occur. (C) 1997 Wiley-Liss, Inc.