Deleterious effect of dithizone-DMSO staining on insulin secretion in rat and human pancreatic islets

Dithizone (DTZ) is a selective stain for pancreatic islets which facilitates their identification, being of special interest in human islet isolation assessment. Nevertheless, there are few studies concerning its potential toxic effects on islet function. In our study, we have evaluated the effects of DTZ (dissolved in dimethyl sulfoxide [DMSO] 1% w/v) at three different concentrations (2, 10, and 100 micrograms/ml) on insulin response to glucose in human and rat islets. Likewise, we studied the effect of incubation time, in the presence of DTZ at the above-mentioned concentrations, on insulin release. Only when DTZ was employed at low concentrations and for a short period of incubation (10 min) was there no impairment of pancreatic islet function. Moreover, even at this low concentration, DTZ became deleterious for islet function when the incubation period with the dye was prolonged for 30 min. Culture (24 h) of previously stained islets produced a partial recovery of insulin response. In conclusion, our findings indicate (a) DTZ should not be employed to collect islets for functional studies because of its deleterious effect on beta-cell function, (b) DTZ's deleterious effects on beta-cell function should be considered if this dye is used to purify islets by fluorescence-activated cell sorting for transplantation.