Synthesis and transport studies of the intrasyncytial lamina: An unusual placental basement membrane in the little brown bat, Myotis lucifugus
Article first published online: 3 FEB 2005
Copyright © 1987 Wiley-Liss, Inc.
American Journal of Anatomy
Volume 178, Issue 4, pages 387–409, April 1987
How to Cite
Cukierski, M. A. (1987), Synthesis and transport studies of the intrasyncytial lamina: An unusual placental basement membrane in the little brown bat, Myotis lucifugus. Am. J. Anat., 178: 387–409. doi: 10.1002/aja.1001780409
- Issue published online: 3 FEB 2005
- Article first published online: 3 FEB 2005
- Manuscript Accepted: 9 OCT 1986
- Manuscript Received: 2 JUN 1986
The chorioallantoic placenta of Myotis lucifugus undergoes a transition from endotheliochorial to hemochorial. The original maternal endothelial basement membrane is incorporated into the apical portion of the syncytial trophoblast, where it persists until term. This intrasyncytial lamina is separated from the maternal blood by thin ectoplasmic projections of the syncytial trophoblast that project through the lamina and spread over the surface, completely engulfing it. While there appear to be direct channels, at junctions of the ectoplasmic processes, from the maternal blood to the intrasyncytial lamina, perfusion studies using the electron-dense tracers alcian blue, ruthenium red, and Thorotrast show that these channels are physiologically closed. In contrast, lanthanum nitrate was able to gain access to the lamina via the extracellular channels. The endocytic uptake of the tracers was similar. These studies suggest several pathways for substances to cross the ectoplasmic zone and the intrasyncytial lamina. Substances may gain direct access to the lamina via extracellular channels, reach the lamina by vesicular transport, or bypass the lamina completely through fenestrations within the lamina. Autoradiographic studies show that the syncytial trophoblast synthesizes portions of the intrasyncytial lamina, demonstrating its partial fetal origin. How long the original maternal components persist and the functional significance of the intrasyncytial lamina are unknown. Possible functions of the lamina include increased surface area of the apical plasmalemma, selective filtration, structural support, and maintenance of cell polarity.