Pancreatic islet cells are able to maintain constant blood sugar levels whilst being under the influence of variable concentrations of nutrients. Glucose stimulates insulin secretion from islet β-cells but suppresses glucagon (a hormone that raises blood glucose) release from α-cells. Many aspects of insulin production are well characterized but those involved in glucagon secretion have been unclear. In the March 17 Nature Cell Biology, Hisamitsu Ishihara and colleagues at the University Medical Center, Geneva, Switzerland, show that islet β-cell secretion and activation is the main inhibitor of glucagon release from neighboring α-cells (Nature Cell Biology, DOI: 10.1038/ncb951, March 17, 2003).

Ishihara et al. used rat pancreas perfusion models and recombinant adenoviruses to analyze signal transduction and the relationship between islet α- and β-cells. They observed that pyruvate, a glycolytic intermediate and principal substrate of mitochondria, stimulated α-cell glucagon secretion. In addition, they showed that although α-cells have...