The Journal of Membrane Biology

, Volume 61, Issue 2, pp 107–114 | Cite as

3HOH-osmotic water fluxes and ultrastructure of an epithelial syncytium

  • D. A. Brodie
  • R. B. Podesta


Ultrastructural changes associated with osmotically-induced water transport and water permeability were examined in two flatworm species,Schistosoma mansoni andHymenolepis diminuta. The structure of the surface layer of these parasites is unusual in that it is a syncytial epithelial layer that lacks tight junctions and lateral extracellular spaces. The permeability coefficients observed in this study are therefore necessarily associated only with the transcellular route of transepithelial transport. The ultrastructural changes associated with volume transport across the epithelial syncytium were also unusual in that the basally located channels extending distally from the inward-facing membrane into the syncytial layer remained open regardless of the direction of water flow.

Despite the structural differences, most of the features of diffusive (P d ) and osmotic (P osm ) water fluxes across the syncytium resembled those observed in other epithelia: (i) Low water permeability with maximum values of 4.1×10−5 forP d and 9.6×10−5 forPosm.(ii)Posm>P d by 2.0- to 3.2-fold. (iii) Outward water permeability less than inward water permeability. This asymmetry could not be attributed to collapsing channels when net volume transport was directed outward since channels in the syncytium remained open regardless of the direction of water flow. The asymmetry could be explained by tissue contraction or swelling when bathed in anisotonic fluids. (iv)Posm values were not significantly altered by tissue unstirred layers but bothPosm andP d values were underestimated when the bulk fluid was not vigorously stirred.

The lower permeability inS. mansoni relative toH. diminuta may be attributed to the membranous surface coat of the former species.

Key words

Schistosoma mansoni Hymenolepsis diminuta epithelial transport water transport 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Diamond, J.M. 1971. Standing-gradient model of fluid transport in epithelia.Fed. Proc. 30:6–13PubMedGoogle Scholar
  2. Diamond, J.M. 1979. Osmotic water flow in leaky epithelia.J. Membrane Biol. 7:195–216CrossRefGoogle Scholar
  3. Frömter, E., Diamond, J.M. 1972. Route of passive ion permeation in epithelia.Nature (London) 235:9–13CrossRefGoogle Scholar
  4. Hockley, D.J. 1973. Ultrastructure of the tegument ofSchistosoma.Adv. Parasitol. 11:233–305PubMedGoogle Scholar
  5. Lumsden, R.D. 1975. Surface ultrastructure and cytochemistry of parasitic helminth.Exp. Parasitol. 37:267–339CrossRefPubMedGoogle Scholar
  6. Os, C.H. van, Wiedner, G., Wright, E.M. 1979. Volume flows across gallbladder epithelium induced by small hydrostatic and osmotic gradients.J. Membrane Biol. 49:1–20CrossRefGoogle Scholar
  7. Pedley, T.J., Fischbarg, J. 1980. Unstirred layer effects in osmotic water flow across gallbladder epithelium.J. Membrane Biol. 54:89–102CrossRefGoogle Scholar
  8. Phillips, J.E. 1977. Problems of water transport in insects.In: Water Relations in Membrane Transport in Plants and Animals. A.M. Jungreis, T.K. Hodges, A. Kleinzeller and S.G. Schultz, editors. pp. 333–353. Academic Press, New York-LondonGoogle Scholar
  9. Podesta, R.B. 1977a.Hymenolepsis diminuta: Marker distribution volumes of tissues and mucosal extracellular spaces.Exp. Parasitol. 42:289–299CrossRefPubMedGoogle Scholar
  10. Podesta, R.B. 1977b.Hymenolepsis diminuta: Unstirred layer thickness and effects on active and passive transport kinetics.Exp. Parasitol. 43:12–24CrossRefPubMedGoogle Scholar
  11. Podesta, R.B. 1980a. Concepts of membrane biology inHymenolepsis diminuta.In: The Biology ofHymenolepsis diminuta. H.P. Arai, editor. Academic Press, New York-London (in press)Google Scholar
  12. Podesta, R.B. 1980b. Membrane biology of helminths.In: Invertebrate Membrane Physiology. R.B. Podesta, editor. Marcel Dekker, New York (in press)Google Scholar
  13. Podesta, R.B., Mettrick, D.F. 1975.Hymenolepsis diminuta: Acidification and bicarbonate absorption in the rat intestine.Exp. Parasitol. 37:1–14CrossRefPubMedGoogle Scholar
  14. Podesta, R.B., Stallard, H.E., Evans, W.S., Lussier, P.E., Jackson, D.J., Mettrick, D.F. 1977.Hymenolepsis diminuta: Determination of unidirectional uptake rates for nonelectrolytes across the surface epithelial membrane.Exp. Parasitol. 42:300–317CrossRefPubMedGoogle Scholar
  15. Prusch, R.D. 1976. Osmotic and ionic relationships in the freshwater flatworm,Dugesia dorotocephala.Comp. Biochem. Physiol. 54A:287–290Google Scholar
  16. Schafer, J.A., Andreoli, T.E. 1972. Water transport in biological and artificial membranes.Arch. Intern. Med. 129:279–292CrossRefPubMedGoogle Scholar
  17. Thompson, D.P., Bricker, C.S., Pax, R.A. 1980. Biophysical characterization of tegumental and subtegumental compartments inS. mansoni.Proc. Am. Soc. Parasitol. 55:33Google Scholar

Copyright information

© Springer-Verlag New York Inc. 1981

Authors and Affiliations

  • D. A. Brodie
    • 1
  • R. B. Podesta
    • 1
  1. 1.Department of ZoologyUniversity of Western OntarioLondonCanada

Personalised recommendations