ABSTRACT
The β-cell and insulin secretion There are approximately 1 million islets of Langerhans in a normal
adult pancreas and these constitute 1-2% of the gland’s mass. There
are four main cell types in the islets: the predominant B or β cells (producing insulin); A or α cells (glucagon), D or δ cells (somatostatin) and PP cells (pancreatic polypeptide). The principal physiological stimulus
for insulin release is the blood glucose concentration, although
numerous other metabolites, hormones and neural factors also mod-
ulate this process. Glucose concentrations of > 5 mmol/l stimulate
insulin release and β cells are exquisitely sensitive to small changes in extracellular glucose concentrations within a narrow physiological
range.
