Rubidium uptake by mouse pancreatic islets exposed to 6-hydroxydopamine, ninhydrin, or other generators of hydroxyl radicals.

The purpose was to study the toxicity of drugs known to generate free radicals on isolated pancreatic islets. The accumulation of 86Rb+ by mouse pancreatic islets was measured in vitro. Exposing the islets to 6-hydroxydopamine, ninhydrin, or phenazine methosulphate+NADH inhibited the Rb+ uptake, whereas paraquat or acetylphenylhydrazine had no effect. This effect of 6-hydroxydopamine was prevented by either of the hydroxyl radical scavengers, sodium benzoate and mannitol, but not by the non-scavenger, urea; ninhydrin was partially protected against by mannitol but not by benzoate. Protection against 6-hydroxydopamine was also afforded by D-glucose but not by L-glucose or 3-O-methyl-D-glucose; none of the sugars protected against ninhydrin. In damaging islet beta-cells and in being protected against by D-glucose, 6-hydroxydopamine closely resembles the diabetogenic drug, alloxan. It is suggested that protection against alloxan may involve both glucose metabolism and the interaction of glucose with its membrane-located carrier, while protection against 6-hydroxydopamine appears to be unrelated to the hexose carrier mechanism.