DELETERIOUS EFFECT OF DITHIZONE-DMSO STAINING ON INSULIN-SECRETION INRAT AND HUMAN PANCREATIC-ISLETS

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