Cell type-specific and developmentally regulated expression of the AE1 anion exchanger in the chicken chorioallantoic membrane
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Antibodies specific for the chicken AE1 anion exchanger have been used to determine the cell-type specific pattern of expression of this electroneutral transporter in the chick chorioallantoic membrane (CAM) during embryonic development. Immunolocalisation analyses demonstrated that the AE1 anion exchanger accumulated in the basolateral membrane of a subset of cells in both the chorionic and allantoic epithelial layers. Double immunostaining indicated that the AE1-positive cells in the chorionic and allantoic epithelia were also positive for the carbonic anhydrase isoform, CAII, which serves as a marker for the villus cavity (VC) cells of the chorionic epithelium and the mitochondria-rich cells of the allantoic epithelium. Immunoelectron microscopy revealed that AE1 accumulated in extensive projections that extended from the lateral membrane of VC cells towards the adjacent capillary covering cells. These results represent the first demonstration of anion exchanger expression in the chick CAM, and they suggest a role for basolateral AE1 in bicarbonate reabsorption that is required in the embryo for maintaining acid-base balance during development.
KeywordsAE1 anion exchangers Chorioallantoic membrane Carbonic anhydrase Immunochemistry TEM CLSM
We are grateful to Dr. P. J. Linser for the monoclonal antibody against chicken carbonic anhydrase and to Garbini S.p.A. for the fertilised eggs. The skilful technical assistance of Stefano Riccioni and Simonetta Cammertoni is gratefully acknowledged. This study was supported by grants from the University of Camerino.
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