Are There Membrane-Lined Channels through the Trophoblast? A Study with Lanthanum Hydroxide
Transfer experiments by Stulc et al. (1969) gave evidence for the existence of water-filled routes, so-called pores or channels, across the rabbit placenta. Their radius was calculated to be approximately 10 nm. These findings have been confirmed for the guinea pig placenta by Thornburg and Faber (1977) as well as by Hedley and Bradbury (1980). Morphological studies of both placentae, however, failed to demonstrate structural correlates, i.e., membrane-lined pathways across the trophoblast from the maternal lacunar surface to the basal trophoblastic surface that faces the fetal capillaries (Enders, 1965; Firth and Farr, 1977; Kaufmann and Davidoff, 1977). Among large numbers of syncytiotrophoblastic intracellular membrane systems like endoplasmic reticulum, Golgi cisternae, and absorptive tubules, structures with apparent luminal contacts to either surface are missing. In a recent publication, Gammal (1985) described so-called syncytial channels in the rhesus monkey placenta. These structures reported by Gammal are not comparable with those discussed in the present publication for several reasons: the “channels” described by Gammal are lamellar spaces rather than tubular channels, their luminal diameters range from 50 to 100 nm, and these “channels” are restricted to the superficial zone of the syncytiotrophoblast and never reach the basal trophoblastic surface.
Unable to display preview. Download preview PDF.
- Kaufmann, P. (1985) Influence of ischemia and artificial perfusion on placental ultra-structure and morphometry. Contr. Gynecol. Obstet. 13, 18–26.Google Scholar
- Kaufmann, P. and Davidoff, M. (1977) The guinea-pig placenta. Adv. Anat. Embryol. Cell Biol. 53 (2), 1–92.Google Scholar
- Kaufmann, P. and Schroeder, H. (1980) Protein transport across the guinea pig chorioallantoic placenta. XIth Int. Cong. Anat., Mexico City.Google Scholar
- Schroeder, H. and Kaufmann, P. (1980) Do transtrophoblastic channels exist in the guinea-pig placenta. Int. Congr. Physiol. Sci., Szeged.Google Scholar
- Sideri, M., de Virgiliis, G., Rainoldi, R., and Remotti, G. (1983) The ultrastructural basis of the nutritional transfer: evidence of different patterns in the plasma membranes of the multilayered placental barrier. Trophoblast Res. 1, 15–26.Google Scholar
- Simionescu, N. (1981) Transcytosis and traffic of membranes in the endothelial cell. In: International Cell Biology, (ed.), G. Schweiger, Berlin, Springer Publishers.Google Scholar