Glucose induces an acute increase of superoxide dismutase activity in incubated rat pancreatic islets

The activity of superoxide dismutase (SOD), catalase, and glutathione perox idase (GSP) in isolated rat pancreatic islets exposed to high glucose conce ntration for a short period of time (60 min) was determined. High glucose c oncentration (16.7 mM) did not significantly alter catalase activity. GSP a ctivity was increased: by glucose at 5.6 mM, remaining elevated at higher c oncentrations up to 16.7 mill. However, the activity of SOD increased with glucose concentration, and this increment was closely correlated with the r ate of insulin secretion (r = 0.96). High potassium (30 mM) did not increas e SOD activity suggesting that the increase in intracellular ionic calcium concentration does not stimulate this enzyme activity. alpha-Ketoisocaproic acid and pyruvate, which are metabolized through the TCA cycle, did not in crease SOD activity, indicating that the stimulation of SOD activity might be triggered by a factor produced through glycolysis or the pentose phospha te pathway.