 In cases of diabetes, KATP channels cannot function properly, and a marked sensitivity to mild cardiac ischemia and hypoxia results from the cells' inability to adapt to adverse oxidative conditions.The degree to which particular compounds are able to regulate KATP channel opening varies with tissue type, and more specifically, with a tissue's primary metabolic substrate.In pancreatic beta cells, ATP is the primary metabolic source, and the ATP/ADP ratio determines KATP channel activity.