Hi Andrew,

I have measured ROS accumulation in HepG2 and SW872 cells, but not in pancreatic islets. I used DCF-DA and exposed my cells to exogenous H202 for 1hr. Fluorescence measured at 485nm ex 535nm em. If you're interested i can send you a paper which i just published

It depends what ROS you want to measure, how specific it needs to be, and whether you want to measure an acute or chronic change in ROS level. There are some recent reviews about ROS measurements in general, and it is a good starting point although the problem of probe loading or expression in whole islets is not addressed.

From my own experiment, I guess there is no perfect way nor easy answer to your question, but the H2DCFDA and DHE methods suffer from a lack of specificity. For superoxide measurement with DHE, you need to measure the specific product of oxidation, not just the increase in fluorescence. I have tried H2DCFDA without success and prefer not to use it, but others published data obtained with H2DCFDA and DHE (although the effect of glucose on islet ROS production vary from a decrease to an increase depending on the investigator).

What does work fine in my lab for both acute and chronic changes in ROS is to measure the oxidation of cytosolic and mitochondrial roGFP-derived probes (native probe reports thiol oxidation, GRX1 fused probe reports glutathione oxidation, and Orp1-fused probe reports changes in hydrogen peroxide). We also used HyPer, but it is extremely sensitive to pH and you need to use SypHer as a pH probe in parallel experiments if you want to avoid artefacts.

You can check my recent papers for some examples of what we can do. If you want to use H2DCFDA, you could contact Geert Martens at the VUB in Brussels,  for DHE I would ask the group of Pierre Maechler in Geneva.

Good luck.