The Journal of Membrane Biology

, Volume 14, Issue 1, pp 17–32

Iodination (125I) of the apical plasma membrane of toad bladder epithelium: Electron-microscopic autoradiography and physiological effects

  • Judy M. Strum
  • Isidore S. Edelman


The apical plasma membrane of toad bladder epithelial cells has been enzymatically iodinated, using lactoperoxidase, H2O2 (generated by a glucose-glucose oxidase system) and NaI. The site of labeling was demonstrated by electron-microscopic autoradiography; the silver grains (125I) were found exclusively overlying the luminal plasma membranes of the epithelium. The iodination reaction reached completion in less than 5 min. The dependence of the degree of iodination on NaI concentrations (range=6.3×10−8 to 6.3×10−2m) in the mucosal medium was determined. The results suggest that three classes of sites are iodinated within this concentration range. At concentrations of NaI of 6.3×10−6m or less, iodination of the apical membrane had no significant effect on either the fine structure of the epithelium or on electrophysiological properties. The baseline short-circuit current (SCC) remained steady and the response to vasopressin was unimpaired. At concentrations of 6.3×10−5m NaI and greater, the baseline SCC was depressed and the response to vasopressin was partially inhibited. The results indicate that125I may serve as a covalent marker (specific for tyrosine and histidine residues) of the apical plasma membrane of epithelia.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Bennet, H. S. 1963. Morphological aspects of extracellular mucopolysaccharides.J. Histochem. Cytochem. 11:14Google Scholar
  2. Bogoroch, R. 1969. Studies on the intracellular localization of tritiated steroids.In: Autoradiography of Diffusible Substances. L. J. Roth and W. E. Stumpf, editors. p. 99. Academic Press, Inc., New YorkGoogle Scholar
  3. Caro, L. G., van Tubergen, R. P. 1962. High resolution autoradiography. I. Methods.J. Cell Biol. 15:173PubMedGoogle Scholar
  4. Forberg, S., Odeblad, E., Soremark, R., Ullberg, S. 1964. Autoradiography with isotopes emitting internal conversion electrons and Auger electrons.Acta Radiol. Ther. Phys. Biol. 2:241Google Scholar
  5. Handler, J. S., Preston, A. S., Orloff, J. 1969. The effect of aldosterone on glycolysis in the urinary bladder of the toad.J. Biol. Chem. 244:3194PubMedGoogle Scholar
  6. Hubbard, A. L., Cohn, Z. A. 1971. Enzymatic iodination of plasma membrane.Abstr. Eleventh Annual Meeting Amer. Soc. Cell Biol., November, 1971, p. 132Google Scholar
  7. Hubbard, A. L., Cohn, Z. A. 1972. Enzymatic iodination of the red cell membrane.J. Cell Biol. 55:390PubMedGoogle Scholar
  8. Ito, S., Winchester, R. J. 1963. The fine structure of the gastric mucosa in the bat.J. Cell Biol. 16:541PubMedGoogle Scholar
  9. Kayes, J., Maunsbach, A. B., Ullberg, S. 1962. Electron microscope autoradiography of radioiodine in the thyroid using the extra-nuclear electrons of I125.J. Ultrastruct. Res. 7:339PubMedGoogle Scholar
  10. Klebanoff, S. J. 1967. Iodination of bacteria: A bactericidal mechanism.J. Exp. Med. 126:1063PubMedGoogle Scholar
  11. Koefoed-Johnsen, V., Ussing, H. H. 1958. The nature of the frog skin potential.Acta Physiol. Scand. 42:298PubMedGoogle Scholar
  12. Lowry, O. H., Rosebrough, N. J., Farr, A. L., Randall, R. J. 1951. Protein measurement with the Folin phenol reagent.J. Biol. Chem. 193:265.PubMedGoogle Scholar
  13. Luft, J. H. 1961. Improvements in epoxy resin embedding methods.J. Biophys. Biochem. Cytol. 9:409PubMedGoogle Scholar
  14. Mamelak, M., Wissig, S. L., Bogoroch, R., Edelman, I. S. 1969. Physiological and morphological effects of poly-L-lysine on the toad bladder.J. Membrane Biol. 1:144Google Scholar
  15. Morrison, M., Bayse, G. S. 1970. Catalysis of iodination by lactoperoxidase.Biochemistry 9:2995PubMedGoogle Scholar
  16. Morrison, M., Bayse, G., Danner, D. J. 1970. The role of mammalian peroxidase in iodination reactions.In: Biochemistry of the Phagocytic Process. J. Schultz, editor. pp. 51–66. North-Holland Publishing Co., AmsterdamGoogle Scholar
  17. Phillips, D. R., Morrison, M. 1970. The arrangement of proteins in the human erythrocyte membrane.Biochem. Biophys. Res. Commun. 40:284PubMedGoogle Scholar
  18. Ussing, H. H., Zerahn, K. 1951. Active transport of sodium as the source of electrical current in the short-circuited isolated frog skin.Acta Physiol. Scand. 23:110PubMedGoogle Scholar

Copyright information

© Springer-Verlag New York Inc. 1973

Authors and Affiliations

  • Judy M. Strum
    • 1
  • Isidore S. Edelman
    • 1
  1. 1.Cardiovascular Research Institute and Departments of Medicine, and of Biochemistry and Biophysics of the University of California School of MedicineSan Francisco

Personalised recommendations