Ultrastructure and membrane permeability of cultured pancreatic beta-cells exposed to alloxan or 6-hydroxydopamine.

Stereological techniques on electron microscopy micrographs were used to evaluate the morphological changes of cultured islet beta cells that had been exposed to alloxan or 6-hydroxydopamine. Trypan Blue exclusion by cells cultured for 3 days indicated that the cells were 100% viable. Electron microscopy revealed that nearly all of the surviving cultured cells were beta cells. Exposure to 5 mmol/l alloxan or 1-5 mmol/l 6-hydroxydopamine for 10 or 30 min caused a general swelling of the cultured cells with a concomitant swelling of mitochondria and nuclei. The size of the secretory granules was not affected by the drugs. Only 3-10% of the cells excluded Trypan Blue after exposure to 5 mmol/l alloxan or 6-hydroxydopamine. The data conform with the hypothesis that a primary action of alloxan and 6-hydroxydopamine is at the plasma membrane level of beta cells.