TRYPAN BLUE AS A MARKER OF PLASMA-MEMBRANE PERMEABILITY IN ALLOXAN-TREATED MOUSE ISLET CELLS

Suspensions of pancreatic islet cells from noninbred ob/ob-mice were incubated with Trypan Blue. Microscope photometry showed that apparently viable cells excluded the dye completely, whereas the nuclei of nonviable cells accumulated Trypan Blue by a saturable process. The nucleus-to-medium dye gradient was more then 30∶1 in media containing 0.1% or less Trypan Blue. The apparent affinity constant for nuclear binding of the dye was 3.1 × 104 l/mol. Albumin partially inhibited the nuclear staining. More than 0.5% Trypan Blue in the medium was toxic per se. In the absence of albumin, 0.5 or 20 mmol/l alloxan, 1 mmol/l N-ethylmaleimide, or 0.1 mmol/l chloromercuribenzene- p-sulphonic acid, but not 20 mmol/l streptozotocin, increased the frequency of islet cells stained with 0.1% Trypan Blue. The absorbance of nuclei was also increased in cells treated with alloxan or N-ethylmaleimide, but not in those treated with chloromercuribenzene- p-sulphonic acid. It is concluded that alloxan rapidly increases the permeability of the plasma membrane in mouse β-cells. This action of alloxan appears to be more acute than any such effect of streptozotocin. © 1978, Italian Society of Endocrinology (SIE). All rights reserved.