The Journal of Membrane Biology

, Volume 112, Issue 2, pp 123–129 | Cite as

Fusion of liposomes and rat brain microsomes examined by two assays

  • Lanfranco Corazzi
  • Giuseppe Fratto
  • Roberto Pistolesi
  • Giuseppe Arienti


Liposomes are prepared from rat brain microsomal lipid and loaded with either Tb3+ or dipicolinic acid (DPA) to test fusion with the Tb-DPA assay. They are also loaded with octadecyl Rhodamine B chloride (R18) to test fusion with the R18 assay. The addition of either Ca2+ or Mg2+ to loaded liposomes develops fluorescence with both assays. The fluorescence elicited by Mg2+ is similar to that elicited by Ca2+ if assessed with R18, but much higher if determined by Tb-DPA. The Ca2+-dependent fluorescence of the Tb-DPA complex is not suppressed by the addition of EDTA, and therefore it is internal to vesicles. The contrary is true for the Mg2+-dependent fluorescence. Rat brain microsomes can be disrupted by adding octylgucoside and reconstituted by removing it by dialysis. We use this procedure to load microsomes with DPA. This allows the use of the Tb-DPA assay for testing the fusion of rat brain microsomes. Reconstituted microsomes fuse with liposomes. This fusion has characteristics similar to those of liposome-liposome fusion. However, no microsome-microsome fusion could be detected with either method. The two methods give different results, owing to the chemical properties of the assays. Indeed Tb-DPA implies the retention of vesicle content, whereas this is not required by the R18 assay.

Key Words

liposomes microsomes fusion membranes brain octadecyl rhodamine 


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Copyright information

© Springer-Verlag New York Inc 1989

Authors and Affiliations

  • Lanfranco Corazzi
    • 1
  • Giuseppe Fratto
    • 1
  • Roberto Pistolesi
    • 1
  • Giuseppe Arienti
    • 1
  1. 1.Department of Experimental Medicine and Biological ChemistryThe University of PerugiaPerugiaItaly

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