Alloxan distribution (in vitro) between cells and extracellular fluid

¹ Department of Anatomy, Western Reserve University School of Medicine, Cleveland, Ohio; Department of Anatomy, University of Minnesota School of Medicine, Minneapolis, Minnesota, and Marine Biological Laboratory, Woods Hole, Massachusetts

The distribution of alloxan added to toadfish tissues in vitro was studied under conditions in which the rate of alloxan decomposition was markedly reduced (0 C, pH 7.0). When washed red blood cells were added to alloxan solutions of varying tonicities, the amount of swelling corresponded to that obtained with equivalent solutions of saline or phosphate; therefore alloxan behaved like a nonpenetrating solute. Alloxan-2-C¹⁴ (tracer doses) was added to blood, and the cells and serum were subsequently separated; the amount of radioactivity in the packed cell mass was identical to that found with d-mannitol-1-C¹⁴, but was far less than that obtained with urea-C¹⁴. Similarly, when toadfish islet slices were incubated in a mixture of alloxan-2-C¹⁴ plus d-mannitol-1-H³, the proportion of the two isotopes found within the tissue was the same as that in the medium. These results indicate that alloxan, like mannitol, does not enter the cells but remains in the extracellular fluid; they thereby support the thesis that the primary site of alloxan action is at the ß-cell membrane.

Key Words: alloxan diabetes • ßbeta; cell • islets of Langerhans • cell membrane • extracellular space • permeability diabetes • cytotoxin • alloxan, mechanism of action

Submitted on November 7, 1963