Static insulin secretion

Pancreatic islets were isolated by collagenase digestion of the exocrine pancreas. Groups of four islets were first incubated for 30 min at 37°C in Krebs’ bicarbonate solution containing 115 mM NaCl, 5 mM KCl, 10 mM NaHCO₃, 2.56 mM CaCl₂, 1 mM MgCl₂ and 15 mM HEPES; supplemented with 0.3% (w/v) bovine serum albumin (BSA) and 5.6 mM glucose; and equilibrated with 95% O₂: 5% CO₂, pH 7.4. After 30 min, the solution was replaced with fresh buffer, and the islets were further incubated for 1 h in the presence of 2.8 or 16.7 mM glucose. At the end of the incubation period, the insulin content of the medium was measured by radioimmunoassay (Ribeiro et al. 2010).